US Democratic senators have unveiled a bill to impose extensive sanctions on top Russian government and military officials, including President Vladimir Putin, as well as key banking institutions in the event that Moscow begins military action against Ukraine, Reuters reported.

The proposed law, backed by the White House, includes provisions to help strengthen Ukraine's security and calls on the United States to consider all available and appropriate measures to ensure that the Nord Stream 2 pipeline is not put into operation.

"This legislation makes it absolutely clear that the US Senate will not stand idly by as the Kremlin threatens a re-invasion of Ukraine," Senator Robert Menendez, the Democratic chairman of the Senate Foreign Relations Committee who unveiled the bill, said in a statement.

More than two dozen Democrats, including Majority Leader Chuck Schumer, have endorsed the bill, a Menendez spokesperson said.

The bill would "trigger severe costs to Russia's economy" if Russia goes ahead with an invasion, a spokesperson for the White House's National Security Council said.

Other legislation, such as a bill sponsored by Republican Senator Ted Cruz, will "not counter further Russian aggression or protect Ukraine," the NSC spokesperson said.