President Joe Biden announced Wednesday that the United States will join Germany in imposing sanctions on the Russian Nord Stream 2 natural gas pipeline project in retaliation for Moscow's mounting military pressure against Ukraine.

The targeting of Nord Stream 2 -- one of energy-rich Russia's highest-profile geostrategic initiatives -- adds to Western sanctions announced by the United States and European allies this week against two Russian banks, several oligarchs and other measures.

Built to funnel Russian natural gas to Germany under the Baltic sea -- bypassing the current overland route which traverses Ukraine -- Nord Stream 2 has long been controversial. It is completely built, but has not been put in use.

"I have directed my administration to impose sanctions on Nord Stream 2 AG and its corporate officers," Biden said in a statement, after Germany announced it was halting the project on Tuesday.

Although the pipeline is seen as an efficient way to supply energy to the European Union, which depends heavily on Moscow, critics say it also would tighten Russia's strategic grip on European nations, while deliberately weakening Ukraine.

The White House had previously blocked attempts by Congress to impose sanctions against the pipeline, saying that construction was already more than 90 percent complete by the time Biden took office and that ally Germany was keen for the project to be completed.

However, with Russia shocking the world by massing troops on Ukraine's border and Western leaders now saying an invasion is already underway, both Berlin and Washington abruptly shifted position.

Coming on top of Germany's earlier decision to block legal certification, the US sanctions doom the project, according to Washington.

"By acting together with the Germans how we did, when we did, and the way in which we did, we have ensured that this is an $11 billion prize investment that is now a hunk of steel, sitting at the bottom of the sea," State Department spokesman Ned Price said.

In his statement, Biden praised Germany as "a leader" on the issue and said that "as I have made clear, we will not hesitate to take further steps if Russia continues to escalate."

"Through his actions, President Putin has provided the world with an overwhelming incentive to move away from Russian gas and to other forms of energy," Biden said.

However, in the shorter term, there are fears that the closing of Nord Stream 2 will prompt Russia to use its resources to squeeze Europe's already hard-pressed energy markets, as well as prompting higher fuel prices in the United States, where Biden faces strong political headwinds over inflation.