The top Republican and Democrat on the House Armed Services Committee are calling for $1 billion in lethal defensive aid to Ukraine.

Texas Rep. Mac Thornberry and Rep. Adam Smith of Washington state introduced legislation on Tuesday to assist the national security forces of Ukraine with training, equipment and lethal defensive weapons.

The move reflects the increased pressure on President Barack Obama to help Ukraine defend itself against Russian-backed rebels.

Obama is considering sending lethal aid to Ukraine's military. The president spoke Tuesday with the leaders of both Russia and Ukraine, one day before they meet for highly-anticipated peace talks.

The White House said Obama reiterated U.S. support for Ukraine's sovereignty in his call with Russian President Vladimir Putin, and emphasized the importance of reaching a diplomatic resolution.