German Foreign Minister Frank-Walter Steinmeier on Thursday argued against arming Ukraine during a trip to Washington where support is growing for delivering weapons to help Kiev battle pro-Russian separatists.

"I understand that many of you are calling for a more rapid, therefore determined, therefore military-based solution," Steinmeier said at an event organized by the Center for Strategic and International Studies, a think-tank.

But providing Kiev with lethal military aid could "catapult the conflict into a next phase" and trigger a "dangerous permanent escalation" between Ukraine and Russia, he warned.

"This can be in nobody's interest."

His visit comes as US President Barack Obama is under pressure not just from hawks in Congress but also from within his own administration to supply the outmatched Ukrainian army with weapons to shore up its faltering defenses.

Obama's new defense secretary Ashton Carter told the Senate in his confirmation hearing last month that he was "very much inclined" towards providing weapons to Kiev.

The US military's top-ranking officer, General Martin Dempsey, said last week that "we should absolutely consider lethal aid and it ought to be in the context of NATO allies."

Germany and many European nations believe Western arms would not offset the military advantage enjoyed by pro-Russian forces allegedly backed by Moscow, and instead would simply fuel a conflict that has claimed an estimated 6,000 lives.

The White House on Wednesday also played down the idea of sending lethal military assistance, stressing that this would "lead to greater bloodshed."