US Congress will write legislation obliging the Pentagon to supply Ukraine with arms, if President Barack Obama does not move to send weapons, Republican Senator John McCain said on Thursday.

McCain led a bipartisan group of US senators at a news conference in pressing the Obama administration to send arms to the war-torn country, fighting a bloody civil war in its east against anti-Kiev rebels.

“United States must act with urgency to provide defensive lethal assistance to Ukraine,” McCain said.

McCain pointed that willingness to provide weapons to Kiev was an “overwhelming bipartisan consensus,” and that the Senate Armed Services Committee (SASC) members will work on a legislation to call for the action again.

“Such defensive weapons could include anti-tank weapons and counter-battery radar systems,” US Senator Jack Reed said.

The United States should not be the only provider of weapons, however, SASC members pointed, adding that the country should work on this issue together with North Atlantic Treaty Organization (NATO) allies.

On Wednesday US Defense Secretary nominee Ashton Carter also said that he supported sending lethal weapons to Kiev.

Deputy National Security Advisor Ben Rhodes however announced earlier that supplying weapons was not the way to end the Ukrainian crisis.

The armed conflict in eastern Ukraine began in April 2014, when Kiev-led forces launched a military operation against the region’s mostly Russian-speaking independence supporters who opposed Ukraine’s new post-coup government.