US senators joined together Tuesday to express a "message of solidarity" to the Ukrainian people and a warning to Russia's Vladimir Putin, although the chamber failed to agree on drafting sanctions against Moscow.

"In this dark hour, we are sending a bipartisan message of solidarity and resolve to the people of Ukraine, and an equally clear warning to Vladimir Putin and the Kremlin," 12 senior Democratic and Republican members of the Senate said in a statement.

The text, signed by the chamber's party leaders Chuck Schumer and Mitch McConnell, marked a rare point of political unity in a hyper-polarized Congress.

But the statement does not carry the weight of law, and comes after political rivals in the evenly divided Senate failed to reach agreement on a bipartisan bill to severely sanction Russia should it invade neighbor Ukraine.

Democrat Bob Menendez, chairman of the Senate Foreign Relations Committee, slammed Senate Republicans for having 'decided to choose partisan posturing instead of working to reach consensus on a comprehensive bipartisan proposal,' on sanctions for Russia i
Democrat Bob Menendez, chairman of the Senate Foreign Relations Committee, slammed Senate Republicans for having 'decided to choose partisan posturing instead of working to reach consensus on a comprehensive bipartisan proposal,' on sanctions for Russia if it attacks Ukraine. GETTY IMAGES NORTH AMERICA via AFP / Drew Angerer

Late last month key senators on both sides of the aisle were close to reaching a deal on sanctions. But late Tuesday Republicans essentially balked by introducing their own sanctions bill -- without Democrats -- for consideration.

"It's a shame that Senate Republicans have decided to choose partisan posturing instead of working to reach consensus on a comprehensive bipartisan proposal," fumed Democrat Bob Menendez, chairman of the Senate Foreign Relations Committee.

US President Joe Biden said Tuesday that Washington was primed and ready with "powerful sanctions" on Russia, although those do not specifically require authorization from Congress.

But cross-party support from lawmakers in the House and Senate would send a strong signal to the Democratic president.

In their joint statement, the senators nevertheless said they were prepared to "fully support" imposing "strong, robust, and effective sanctions on Russia."