WASHINGTON — After meeting with the leader of Germany, President Biden said on Monday that a lucrative gas pipeline project connecting Russia and Germany would not go forward if Moscow invades Ukraine.
Mr. Biden vowed that Germany and the United States would take a “united” approach to rising tensions between Russia and Ukraine, despite concerns that Germany has not been a forceful enough partner in confronting Russia.
“If Russia makes a choice to further invade Ukraine we are jointly ready,” Mr. Biden said, standing beside Chancellor Olaf Scholz at the White House, “and all of NATO is ready.”
Their meeting, the first since Mr. Scholz took office in December, was designed to publicly shore up a key link in the Western alliance as it faces one of its gravest challenges since the Cold War, with President Vladimir V. Putin of Russia massing more than 100,000 troops near Ukraine’s borders.
Among the main concerns ahead of the meeting, Mr. Biden’s advisers said, was Mr. Scholz’s reluctance to sign onto punishing economic sanctions in the event of an invasion, or to call off the gas pipeline project, Nord Stream 2.
On Monday, Mr. Biden, who has refrained publicly criticizing Mr. Scholz, said that the Germans supported a “strong package” of sanctions but did not detail what those would be. In recent weeks, Mr. Biden has threatened severe economic sanctions against Russia’s financial sector and members of Mr. Putin’s inner circle. On Nord Stream 2, Mr. Biden said that the project would not go forward should Russia invade.
Mr. Biden defined invasion in the most traditional terms possible — troops and tanks — not addressing a number of other ways his aides fear Mr. Putin could bring the country to its knees, including organizing a coup or launching crippling cyberattacks.
“If Russia invades, that means tanks and troops crossing the border of Ukraine again, then there will be no longer a Nord Stream 2,” Mr. Biden said. “We will bring an end to it.”
When asked exactly how, Mr. Biden said, “I promise you we’ll be able to do it.”Mr. Scholz, asked the same question, did not answer as forcefully. He has been vague about whether he would agree to terminate the pipeline project, but on Monday he repeated what he has said frequently: “We are absolutely united.”
It has been a rocky first few months on the job for Mr. Scholz, who took over from Angela Merkel, who had worked with four U.S. presidents. Berlin’s reluctance to join in outlining consequences for Russia if it invades Ukraine strained relations to the point that last week the German ambassador in Washington sent a warning home that many in the United States see Germany as an “unreliable partner.”
Mr. Biden forcefully swatted away that notion.
“There’s no need to win back trust,” Mr. Biden said. “He has the complete trust of the United States.”
The situation represents a diplomatic pivot for Mr. Biden, who extolled his relationship with Ms. Merkel in a meeting at the White House in July: “Good friends can disagree” on matters including how each conducted relations with Russia, he said at the time. More than six months later, Mr. Biden is determined to present a united NATO front in the Ukraine crisis; administration officials say that the Russian military has already assembled 70 percent of the forces it would need to mount a full-scale invasion.
In a call with reporters on Sunday, administration officials said that Mr. Biden would be looking to discuss a package of “swift and severe” sanctions against Russia if Mr. Putin decides to invade Ukraine; the Kremlin insists that no such action is contemplated.
Understand the Escalating Tensions Over Ukraine
“I don’t know that he knows what he is going to do,” Mr. Biden said. He added, “I have been very very straightforward and blunt with President Putin both on the phone and in person: We will impose the most severe sanctions that have ever been imposed.”
Given the risk of war, Mr. Biden advised American civilians in Ukraine to leave the country, adding that he would “hate to see them get caught in the crossfires.”
In comparison, Mr. Scholz’s relatively vague stance that has drawn criticism from both Republicans and Democrats: “The Germans are right now missing in action,” Senator Richard Blumenthal, Democrat of Connecticut, who visited Ukraine in January, said recently. Senator Rob Portman, Republican of Ohio, has publicly criticized Germany for not allowing flights carrying military aid for Ukraine to fly through German airspace.
Nord Stream 2 , an $11 billion natural gas conduit being built between Germany and Russia, has been assailed by Mr. Biden and his advisers as a coercive tool against Ukraine and other allies, even though the president agreed last year to waive sanctions related to the project.
The pipeline is on hold as European Commission officials investigate whether the project is in compliance with European energy policy.
Next week, Mr. Scholz will visit Kyiv and Moscow, following a visit to both cities from Emmanuel Macron, the president of France.
Germany has declined to sell Ukraine weaponry or ammunition, citing a longstanding policy of not contributing to ongoing conflicts. Speaking at a news conference on Monday, Ukraine’s foreign minister, Dmytro Kuleba, said he intended to raise the issue with Germany’s foreign minister, Annalena Baerbock.
Andrew E. Kramer contributed reporting from Kyiv, Ukraine.