US President Barack Obama will "soon" decide whether to give Kiev arms to fight pro-Russian rebels but prefers a diplomatic solution, Secretary of State John Kerry said in Kiev on Thursday.

US President Barack Obama will "soon" decide whether to give Kiev arms to fight pro-Russian rebels but prefers a diplomatic solution, Secretary of State John Kerry said in Kiev on Thursday.

"The president will make his decision, I'm confident, soon," Kerry told journalists after the White House signalled it may be ready to provide weapons, adding that "the first preference is obviously to be able to resolve this through diplomacy."

US Secretary of State John Kerry on Thursday flew in to Kiev where Ukraine's pro-Western leaders hope Washington will send in weapons for their battle against separatists.

Ukraine and its Western allies accuse Moscow of sending thousands of regular army troops and weapons to support the rebels who launched an uprising against Kiev in April. However, Moscow has repeatedly denied the allegations.

The fighting has claimed more than 5,358 lives since April, including some 220 in just the past three weeks, according to the United Nations.