The president of Ukraine has asked the US to give his soldiers lethal military equipment in its battle against Russian-backed separatists.
US president Barack Obama has so far resisted Ukraine’s request for lethal assistance. The US has provided about $60m in non-lethal aid.
President Petro Poroshenko spoke to a joint meeting of Congress.
Ukraine and the separatists are battling for control of eastern Ukrainian cities on Russia’s border.
The Ukrainian parliament passed a law granting the rebel strongholds greater autonomy. Rebel leaders insist on full independence from Ukraine.
The crisis followed Russia’s annexation of the Crimean peninsula, which Mr Poroshenko said was one of the most “cynical acts of treachery in modern history”.