President Trump, speaking at the NATO summit in Europe Wednesday morning, said he believes Germany is "captive to" and "totally controlled" by Russia because of the planned Nord Stream 2 gas pipeline.

Be smart, from Axios' future editor Steve LeVine: This is the sound of a natural gas war. Trump wants Germany — an enormous gas purchaser — to buy American liquefied natural gas and is attempting to steal the market now held by Russia.

The details: Nord Stream 2 is an expansion of an existing pipeline, Nord Stream 1, that already transports some gas from Russia to Germany, per the WSJ. This controversial second phase would go live in 2019.

• The pipeline would likely boost Russia’s authority in Europe when it comes to gas deliveries, according to Ukraine and other European allies. CNBC's Natasha Turak has also written that the pipeline would “increase Germany’s reliance on Russian energy supply.”
• Nord Stream 2 also runs counter to the EU's energy security strategy, which it outlined in 2014 with a focus on diversity, according to The Atlantic Council.

What Trump's saying: The president has warned that if Germany wants to develop a trade deal with the U.S., it would be dependent on whether Germany drops its Nord Stream 2 plans with Russia.

• But Germany has said previously that calling the deal off is not legally possible, since all the permits for the pipeline have been issued, per the WSJ.
• Meanwhile, the State Department’s Dandra Oudkirk has signaled that companies involved in the pipeline project could be subject to U.S. sanctions.

What they’re saying:

• German Chancellor Angela Merkel fired back at Trump, stating that while part of Germany used to be controlled by Soviet Russia, it is not anymore.
• Defense Minister Ursula von der Leyen told CNBC that “Germany is an independent country where energy supply is concerned, we diversify.”