Biden, German chancellor present united front amid tensions with Russia over Ukraine

President Joe Biden welcomed German Chancellor Olaf Scholz to the White House Monday at a critical time for the leaders as tensions with Russia persist over Ukraine.

During brief remarks in the Oval Office ahead of a joint press conference, Biden said the two countries are "working in lockstep to further deter Russian aggression in Europe and address the challenges opposed by China and promote stability in the Western Balkans," as military forces buildup along the Ukraine border.

Monday marks Scholz's first visit to the White House, and Biden said it provided a good chance to "get to know you more personally."

While the Biden administration has warned for weeks that Russia will face "severe" consequences if it invades Ukraine, Germany had often opted for a softer response, refusing to send military equipment to Ukraine or deploy more troops to the eastern flank. Germany had also shown reluctance to shut down Nord Stream 2, a Russian natural gas pipeline, not yet operational, that would carry gas directly to Germany, bypassing Ukraine.

Meanwhile, Biden has been rallying European allies to respond to Russia's threats in lockstep with his more aggressive plan. But meeting with Scholz Monday, the two world leaders expressed unity with their posture towards Russia.

After both leaders appeared to avoid mentioning the pipeline, under repeated questions from reporters at an afternoon press conference, Biden, standing next to the German chancellor said Nord Stream 2 would not move forward if Russia invades Ukraine, in a warning to Russian President Vladimir Putin of potential economic consequences.

"If Russia invades, that means tanks or troops crossing the -- the border of Ukraine again, then there will be -- there will be no longer a Nord Stream 2," Biden said during the press conference with Scholz, who did not go as far as Biden, but insisted the U.S. and Germany remain "absolutely united."

Pressed on how he can commit to that given that Nord Stream 2 is under German control, Biden doubled down, saying, "We will -- I promise you -- we will be able to do it."

Scholz, in turn, expressed unity with the U.S. and said that Germany was preparing sanctions in case Putin decides to invade.

"As I already said, we are acting together," Scholz said at the press conference. "We are absolutely united and we will not take different steps. We will do the same steps and they will be very, very hard to Russia, and they should understand."

Biden added that all diplomatic lanes should be taken to de-escalate the situation on the Ukraine border where at least 100,000 Russian troops have gathered and that Russia needs to understand NATO nations stand together.

Asked by another reporter if Americans who are still in Ukraine should leave, Biden said would be "wise" for Americans to leave the country.

“I’m not talking about our diplomatic core. I'm talking about Americans who are there. I hate to see them get caught in a crossfire if, in fact, they did invade. And there's no need for that," Biden said.

ABC News Chief White House Correspondent Cecilia Vega asked Biden as he was exiting the press conference, "Is de-escalation possible?"

"The answer is yes," Biden replied.

While an administration official earlier acknowledged "the narrative that's been out there" that Germany's response to Russia has been lacking, they were not outright critical of Scholz's hesitation thus far. But they declined to say whether U.S. officials have already convinced the Germans to get on board with the plan to block Nord Stream 2 entirely if Putin decides to move.

"We're confident that the Germans share our concerns with Russian aggression, that they're very involved in our ongoing efforts on both deterrence and diplomacy," the official said. "What I can say is that we will continue to work very closely with Germany to ensure the pipeline does not move forward."

When asked if the administration is working on ways to prevent the Nord Stream pipeline from becoming operational regardless of if Russia invades, the official underscored the U.S. opposition to the project overall, ahead of Biden's joint remarks.

"There is not currently any gas flowing through the pipeline. And there won't be any gas for months, in part because of the diplomacy that the United States has been able to do on this issue with Germany," the official noted.

ABC News has learned Putin now has 70% of the troops necessary to possibly launch a full-scale attack on Ukraine in place along the Ukrainian border. With U.S. intelligence indicating Putin is preparing for a large-scale invasion, the senior administration official said key allies like Germany are being kept aware of the situation.

"I absolutely think that our countries are unified in terms of awareness of the risk of further Russian aggression to Ukraine. We have been for a long time sharing intelligence with Germany with the rest of our allies," the official said. "And I think there is absolutely absolute agreement, that if there is further Russian aggression, that there's a number of things that need to be done in terms of deployment of additional troops to the eastern flank, and to the imposition of a large package of economic sanctions."

Scholz's visit comes almost two months to the day since he took office, highlighting the importance of the U.S.-German relationship.

Biden first met with Scholz in October at the G-20 summit, when former Chancellor Angela Merkel invited the then-finance minister to accompany her to her meeting with Biden, giving the leaders a chance to meet ahead of Scholz taking the helm.

As Biden and Scholz participated in their first joint press conference from the East Room, in-person talks between French President Emmanuel Macron and Putin wrapped after five hours, according to Russian media.

Biden told reporters Monday that he has been “very straightforward and blunt” in his discussions with Putin when warning of sanctions Russia could face but said he still he does not know what Putin will ultimately do.

“I know he's in a position now to be able to invade, almost assuming that the ground is frozen above Kiev. He has the capacity to do that," Biden said. "What he's going to do, I don't know."