As a bipartisan push for sanctions against Russia stalls in Congress, Republicans present their own bill.

WASHINGTON — A bipartisan effort in to authorize a bruising set of sanctions against Moscow sputtered on Capitol Hill on Tuesday, as lawmakers conceded that they were unlikely to reach agreement on any new legislation and Republicans introduced their own bill.

What began last month as an effort to present a unified front on Capitol Hill in favor of pressing the Biden administration to take a tougher stance against Russia has faltered amid disagreements between Democrats and Republicans over just how far to go.

Republicans have pressed for the imposition of sanctions before any invasion of Ukraine. But that, Democrats and the Biden administration have argued, would mean the loss of crucial negotiating leverage that might stave off a military incursion.

By Tuesday,it appeared that the only bipartisan message Congress would be able to muster in the short term was a nonbinding joint statement of support for Ukraineand an admonition to Russia not to invade.

In a statement signed by the Senate majority and minority leaders, Chuck Schumer, Democrat of New York, and Mitch McConnell, Republican of Kentucky, lawmakers pledged to “fully support the immediate imposition of strong, robust, and effective sanctions on Russia” in the event Moscow authorized an invasion.

“Make no mistake: the United States Senate stands with the people of Ukraine and our NATO allies and partners most threatened by Russian aggression,” the senators said. “Our troops stand ready to reinforce the defenses of our Eastern European allies and we are prepared to respond decisively to Russian efforts to undermine the security of the United States at home and abroad.”

In another sign that bipartisan negotiations were collapsing, Senator Jim Risch of Idaho, the top Republican on the Foreign Relations Committee, introduced his own sanctions legislation. It would target allies of the Russian president, Vladimir V. Putin, and Russian banks ahead of an invasion and impose secondary sanctions in the event Moscow crosses the border. The legislation, co-sponsored by more than 30 Senate Republicans, would also provide the Ukrainian government with an additional $500 million in military financing and authorize President Biden to lend and lease military equipment to Ukraine.

“Rather than simply restating authorities the president already has,” Mr. Risch said, the bill “takes immediate action to permanently stop Nord Stream 2, sends a powerful deterrent message, imposes heavy economic and military costs on Russia, strengthens U.S. allies and partners, and supports Ukraine via new authorities, funds, and tools.”

House Republicans introduced a parallel bill on Tuesday evening. It would also deny the export of semiconductor technology to Russia.

Less than an hour after Senate Republicans unveiled their legislation, the chairman of the Senate Foreign Relations Committee, Bob Menendez, Democrat of New Jersey, denounced the move as “partisan posturing.” He said the G.O.P. proposal was “largely a reflection of what Democrats had already agreed to.”