WASHINGTON—Two senior U.S. Senate Democrats urged President Joe Biden’s administration on March 23 to apply all its diplomatic weight to stop the Nord Stream 2 natural gas pipeline from Russia to Europe, increasing pressure from members of his party.

Sens. Bob Menendez (D-N.J.), the influential chairman of the Senate Foreign Relations Committee, and Jeanne Shaheen (D-N.H.), who chairs the panel’s Europe subcommittee, asked Secretary of State Antony Blinken to implement sanctions under existing laws.

“This pipeline must be stopped and your leadership is required towards that end,” they wrote in a letter.

“We do ... urge that the effort to build strong Nord Stream 2 sanctions packages be accelerated to meet the urgency of the moment,” they said, noting that the pipeline will be completed this year if construction continues unimpeded.

The $11 billion project is about 94% complete and analysts say it could be finished between June and September.

The State Department did not immediately respond to a request for comment.

Nord Stream 2, led by Russia state energy company Gazprom with its Western partners, would take Russian gas to Germany under the Baltic Sea.

The pipeline would bypass Ukraine, likely depriving it of lucrative transit revenues and potentially undermining its efforts to counter Russian aggression.

U.S. companies also want to sell Europe LNG as an alternative to Russian gas, which is usually cheaper.

Close ally Germany needs gas as it weans itself off nuclear and coal.

Blinken said last week that any entities involved with the project “should immediately abandon work.” He will soon meet his German counterpart, Heiko Maas, to discuss the project.

U.S. lawmakers criticized the State Department last month for not sanctioning new companies building the project when it issued a report to Congress. The next report is due in mid-May, though any new sanctions could come ahead of it.