U.S. President Joe Biden reaffirmed Monday that a joint gas pipeline project between Germany and Russia won't advance if Russia invades Ukraine, stopping short of explaining how it will be achieved if Germany has reservations for that decision as a deterrence against Moscow.

With visiting German Chancellor Olaf Scholz standing next to him, Biden told a press conference at the White House that if Russian tanks and troops cross the border and enter Ukraine, "there will be no longer Nord Stream 2," referring to the now-finished pipeline delivering natural gas from Russia to Germany that bypasses Ukraine.

"We will bring an end to it," the president said of the pipeline that is not yet operational.

Asked how the United States will manage to prevent gas from flowing in the pipeline since the project is under Germany's control, Biden didn't elaborate, only saying he can "promise" that Washington "will be able to do that."

Scholz, for his part, repeatedly avoided directly mentioning Nord Stream 2, although it appeared that the pipeline was one of the subjects that most concerned reporters during the press conference.

"We will be united," the chancellor said, speaking in English as if he wanted to give Americans reassurance. "We will act together. And we will take all the necessary steps, and all the necessary steps will be done by all of us together."

Biden and Scholz -- whose ongoing visit in the United States is his first since assuming the chancellorship in December -- were both trying to exhibit the unwavering unity between Washington and Berlin vis-a-vis the handling of the ongoing crisis on Ukraine's borders.

There has been a great deal of frustration expressed by U.S. media and lawmakers on Capitol Hill about Germany's decision not to aid Ukraine with lethal weapons, as well as what they perceived as the lack of clarity from Berlin on whether to turn off Nord Stream 2.

"There's no need for him to win back trust. He has the complete trust of the United States," Biden said in defense of Scholz as the chancellor was challenged by a reporter to rethink whether Germany's decision will make it less of a reliable ally of the United States.

Stressing that the transatlantic partnership with the United States is "one of the permanent pillars of German policy," Scholz said his country has done its part both in terms of strengthening the North Atlantic Treaty Organization's military might and with regard to providing financial assistance to Ukraine.

Further dispelling concerns over Germany's dependence on Russian gas supply, Scholz said his government has been taking measures to accelerate the transition into a clean energy-based economy, noting that one quarter of the total energy that Germany now relies on is generated by gas, "and only part of that gas comes from Russia - big part comes from Norway or The Netherlands."