The Trump administration has a new target on the immigration front — pregnant women visiting from other countries — with plans as early as this week to roll out a new rule cracking down on "birth tourism," three administration officials told Axios' Stef Kight and me.

Why it matters: Trump has threatened to end birthright citizenship and railed against immigrant "anchor babies." The new rule would be one of the first tangible steps to test how much legal authority the administration has to prevent foreigners from taking advantage of the 14th Amendment's protection of citizenship for anyone born in the U.S.

• "This change is intended to address the national security and law enforcement risks associated with birth tourism, including criminal activity associated with the birth tourism industry," a State Department official told Axios.
• The regulation is also part of the administration's broader efforts to intensify the vetting process for visas, according to another senior administration official.

The big picture: "Birth tourists" often come to the U.S. from China, Russia and Nigeria, according to the AP.

• There's no official count of babies born to foreign visitors in the U.S., while the immigration restrictionist group Center for Immigration Studies — which has close ties to Trump administration immigration officials — puts estimates at around 33,000 every year.

How the new regulation would work: It would alter the requirements for B visas (or visitor visas), giving State Department officials the authority to deny foreigners the short-term business and tourism visas if they believe the process is being used to facilitate automatic citizenship.

• It's unclear yet how the rule would be enforced — whether officials would be directed to consider pregnancy or the country of the woman's citizenship in determining whether to grant a visa.
• Consular officers who issue passports and visas "are remarkably skilled at sussing out true versus false claims," the senior official said.
• "The underlying practical issue is that very few people who give birth in the U.S. got a visa for that specific purpose. Most people already have visas and come in later," according to Jeffrey Gorsky, former chief legal adviser in the State Department visa office.

This is but one step in the administration's plans to make it harder for people from other countries to benefit from birthright citizenship.

• "Rome wasn't built in a day," the senior official said. "Just the legal recognition that this is improper and wrong and not allowed is a significant step forward."
• The plans to address the use of B visas for birth tourism were included in the latest version of the Unified Agenda of Federal Regulatory and Deregulatory Actions.
• Immigration experts expect there to be a similar rule for Customs and Border Protection to go along with the State Department's regulation.

What to watch: Most of Trump's major immigration moves have been met with lawsuits. If the regulation leaves it to officers' discretion to ensure that B visas aren't used for birth tourism, it would be difficult to challenge in court, according to Lynden Melmed, an attorney and former chief counsel at U.S. Citizenship and Immigration Services.

• "State Department officials have all the discretion in the world to deny people visas," said Sarah Pierce of the Migration Policy Institute. Foreign nationals who are outside the U.S. and have not yet received visas "don't have a lot of legal standing."
• But specific restrictions that could keep out non-birth tourism visitors — such as pregnant women coming to the U.S. for business, etc. — would be legally questionable, according to Melmed and Gorsky.

Trump officials say they feel especially bullish about one key argument against calling additional impeachment witnesses: It could compromise America's national security.

• People close to the president say their most compelling argument to persuade nervous Republican senators to vote against calling new witnesses is the claim that they're protecting national security, Axios' Alayna Treene and I report.

Why it matters: They're banking on it to speed up the trial, according to people close to the president.

What we're hearing: White House Counsel Pat Cipollone, who considers himself a civil libertarian, is expected to argue that the obstruction of Congress article is dangerous and could forever undermine the power of the executive office to protect privileged information.

• Cipollone will likely frame the Senate trial as a defining moment to set the precedent for executive privilege, especially on national security matters, per a source familiar with his thinking.
• This approach is something Cipollone is particularly proud of, and one that he is happy to test in court, the source said.
• The argument: Presidential claims of executive privilege are especially strong when they involve conversations about national security.
• Weakening that privilege would make presidents less candid when they seek counsel from their advisers on national security (think John Bolton).

The bottom line: Sources close to Trump's legal team have privately expressed confidence that former National Security Adviser Bolton will ultimately honor Trump's assertion of executive privilege.

Senators will almost certainly get to vote on whether or not to call impeachment witnesses, Alayna writes. The resolution laying out the rules of the trial, which will be presented Tuesday, is expected to mandate that senators can take up-or-down votes on calling for witnesses and documents.

Not so fast: Those votes won't come until the House impeachment managers and President Trump's defense team deliver their opening arguments and field senators' questions.

• Moderate Senate Republicans have pushed for this precise language. An aide to Sen. Susan Collins, who faces a tough re-election, told Axios the language is "critical" for her and her campaign.

What to watch: Senate Minority Leader Chuck Schumer is also expected to use the vote on the resolution to push Democrats' messaging, with an eye trained on weakening the GOP majority in the Senate and clawing back the more vulnerable seats in November.

• A Democratic leadership aide told Alayna that Democrats will force votes on subpoenaing key witnesses such as Bolton, acting Chief of Staff Mick Mulvaney, Mulvaney's senior adviser Robert Blair, and top White House budget official Michael Duffey, as well as relevant documents.
• This has concerned some vulnerable Senate Republicans. "The Democratic amendments that will be offered in the beginning will be designed to screw us," a Republican Senate aide told Axios. "Like, 'How can we cut these to look like an ad?'"

"Democrats are going to try and amend these things until the cows come home, but remember, senators can't talk," a GOP leadership aide said. "So there won't be a clip of Susan Collins voting no on this."

• Reality check: Although senators are required to remain silent during the trial, all votes will be recorded.
• "This is not the political silver bullet that Democrats think it will be," the aide added. "Remember that every time Schumer offers up something to tweak our organizing resolution, it's an implicit way of saying that the House investigation came up short."

Meanwhile, a key strategy within the Trump team's defense mechanism is the notion that the articles themselves are not criminal, and therefore are not impeachable offenses, even if proven.

• In turn, they'll claim this is why the debate over witnesses is bogus.
• "If a person is indicted on something that is not a crime, you don't call the witnesses," Alan Dershowitz, a member of Trump's defense team, said earlier today on CNN's "State of the Union."
• Expect to hear this line again.

What to expect:

• Trump's briefs are due 12 p.m. Monday.
• House managers' reply is due 12 p.m. Tuesday.
• The Senate reconvenes at 12:30 p.m. Tuesday. Shortly after that, Senate Majority Leader Mitch McConnell is expected to deliver brief remarks on impeachment.
• The Senate impeachment trial reconvenes at 1 p.m. Tuesday.

Once the trial starts back up, McConnell will immediately introduce a motion on the organizing resolution.

• That will trigger two hours of debate on the resolution. Senators will have an opportunity to offer amendments. This process could drag on for hours, depending on how many amendments are introduced.
• The Senate will then vote on the resolution, after which opening arguments will commence.

Trump is expected to decide in the next several days whether to present the White House's Middle East peace plan before Israel's March 2 elections, Israeli and U.S. sources tell my colleague Barak Ravid.

Why it matters: If the plan is presented before the Israeli elections, it could influence the campaign and possibly provide a boost to embattled Prime Minister Benjamin Netanyahu.

• Netanyahu wants the White House to present the plan before the elections to shift the focus of the campaign away from his corruption cases.
• Benny Gantz, Netanyahu's rival and the leader of the Blue and White Party, has argued that releasing the peace plan ahead of the elections would amount to electoral interference.

Go deeper.

The House is on recess through January 27.

The Senate reconvenes Tuesday at 12:30 p.m., and the impeachment trial will resume at 1 p.m.

President Trump's schedule, per a White House official:

• Tuesday-Wednesday: Trump will be in Davos, Switzerland, for the World Economic Forum.
• Thursday: Trump will speak at the Republican National Committee's winter meeting in Doral, Florida.
• Friday: Trump will deliver remarks on "transforming America's communities."

Former prosecutor Robert Ray knew exactly whom to thank for his new gig as a member of President Trump's impeachment legal team: Fox host Maria Bartiromo.

"On a personal note, thank you very much for all the appearances going back now many, many months," Ray said to Bartiromo at the beginning of his interview on Fox News' "Sunday Morning Futures" this morning.

• "I'm not sure — if not for you, I don't know that I would have come to the president's attention," Ray added.

Between the lines: Truer words have rarely been spoken.