By DONNA CASSATA and DEB RIECHMANN, Associated Press

WASHINGTON (AP) — The top Republican and Democrat on the House Armed Services Committee on Tuesday called for $1 billion in lethal defensive aid to Ukraine as Congress increased pressure on President Barack Obama to help Ukraine defend itself against Russian-backed rebels.

Rep. Mac Thornberry, R-Texas, the panel's chairman, and Rep. Adam Smith of Washington state introduced legislation that would provide training, equipment and lethal defensive weapons to the national security forces of Ukraine through Sept. 30, 2017 to help secure "its sovereign territory against foreign aggressors."

"It seems Russia has decided to go back to the Cold War," Smith told reporters at a news conference, citing Russia's takeover of Crimea and push into eastern Ukraine. The imposition of economic sanctions "has not at all changed President (Vladimir) Putin's calculus."

Thornberry, who joined senators at a defense conference in Munich this past weekend, said "there's a huge amount of bipartisan support to allow the Ukrainians to defend themselves."

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 talks aimed at reaching an elusive peace deal.

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.

"However, if Russia continues its aggressive actions in Ukraine, including by sending troops, weapons, and financing to support the separatists, the costs for Russia will rise," the White House said in a statement.

Obama also discussed Wednesday's cease-fire talks in Minsk, Belarus, with Ukrainian President Petro Poroshenko. The peace talks involve the leaders of France, Germany, Russia and Ukraine and come after nearly a year of fighting that the U.N. says has killed more than 5,300 people.

Ukraine and Western nations fault Russian aggression for fueling the rebellion with troops and weapons, a charge Moscow denies.

The bipartisan legislation — and the show of unity by the two senior lawmakers — underscore the growing demand in Congress from both Republicans and Democrats for aggressive action by the U.S.

Last week, Republicans and Democrats called on the administration to provide lethal defensive weapons as well as provide additional non-lethal assistance, including counter-battery radars, unmanned aerial vehicles, electronic counter-measures for use against opposing UAVs, secure communications capabilities, armored Humvees and medical support equipment.

They wrote that the defensive military assistance the U.S. should provide should include light anti-armor missiles "given the large numbers of armored vehicles that the Russians have deployed in Donetsk and Luhansk and the abysmal condition of the Ukrainian military's light anti-armor weapons."