More than 700 children who crossed from Mexico into the United States without their parents were in Border Patrol custody as of Sunday, according to an internal Customs and Border Protection document obtained by Axios.

Why it matters: The current backup is yet another sign of a brewing crisis for President Biden — and a worsening dilemma for these vulnerable children. Biden is finding it's easier to talk about preventing warehousing kids at the southern border than solving the problem.

Rep. Linda Sanchez (D-Calif.) will introduce Biden's immigration bill Thursday, which includes an eight-year pathway to citizenship for millions of undocumented immigrants. Sen. Bob Menendez (D-N.J.) will introduce the bill in the Senate next week.

Why it matters: The bill is unlikely to win needed Republican support, but represents the aggressive immigration priorities of President Biden. It will also kick off the immigration debate on Capitol Hill, which could lead to less sweeping immigration reforms.

Minority Leader Kevin McCarthy (R-Calif.) and other top House Republicans sent a letter to President Biden Wednesday urging him to take up a Trump-era proposal that would increase scrutiny of China's state-funded Confucius Institutes in the U.S., according to a draft first obtained by Axios.

Why it matters: Critics of the Chinese culture and language program say it's a "soft power" tool used to spread Beijing's influence on college campuses. Republicans have accused Biden and his Cabinet nominees of being "soft" on China and are pushing for him to take a harder line.

The Biden administration is urging officials to use more inclusive terms for immigrants, including replacing the word "alien" with "noncitizen," Axios has learned.

Why it matters: The Trump administration referred to unauthorized immigrants as "illegal aliens" and described border crossings as an "invasion." The new terms point to President Biden's more welcoming immigration stance overall.

The Biden administration will soon slowly begin allowing asylum seekers forced to wait in Mexican border towns under former President Trump's "Remain in Mexico" policy to enter the U.S., the Department of Homeland Security announced Friday.

Why it matters: President Biden has promised to end the Trump administration's Migrant Protection Protocols program, as it is formally called, which forced tens of thousands of migrants into dangerous, squalid conditions in Mexico as they awaited court proceedings. DHS estimates that there are about 25,000 migrants in the MPP program who have active immigration court cases.

President Biden informed Congress on Thursday that he has terminated the national emergency over the U.S.-Mexico border that former President Trump first declared in Feb. 2019.

Why it matters: Trump used the national emergency proclamation to divert billions of dollars in Pentagon funds toward building a border wall, after it became clear that Congress was opposed to additional funding. The declaration prompted dozens of lawsuits and attempts by Congress to block Trump from fulfilling one his top 2016 campaign promises.

More than 1,000 foreigners have seen their luck wasted — winning a coveted diversity green card lottery only to see their visas expire because of the coronavirus and former President Trump's immigration ban.

Why it matters: President Biden has been dismantling many of his predecessor's immigration policies, yet some coronavirus-related restrictions remain — threatening at least 6,500 issued visas set to expire by the end of March.

The Senate on Tuesday confirmed Alejandro Mayorkas as Secretary of the Department of Homeland Security, 56-43.

Why it matters: Mayorkas is an Obama administration alum and oversaw the implementation of the Deferred Action for Childhood Arrivals (DACA) program. He will be the first Latino and immigrant to hold the job, which largely oversees immigration issues in the U.S.

President Biden is preparing for his own crisis at the U.S. border, with 5,000 migrant children and counting: The number of unaccompanied minors trying to cross is rising while coronavirus distancing requirements have cut by half the number of useable beds in government shelters.

Driving the news: Two administration officials tell Axios plans are underway to open an overflow shelter in Carrizo Springs, Texas, which could house another 700 children in its main building under COVID-19 precautions.

Chad Wolf, Ken Cuccinelli and Mark Morgan, three of former President Trump's biggest immigration policy defenders, will join the Heritage Foundation on Monday as fellows, Axios has learned.

Why it matters: All three former Homeland Security officials consistently backed Trump and were key in implementing his strict immigration agenda. Now, they will continue to shape conservative policy ideas on national security and foreign policy from the outside.