The United States is reconsidering whether to provide weapons to Ukraine in its fight against Russian-backed separatists, a senior US administration official has said.
"It's getting a fresh look," the official said on Monday, referring to deliberations among Obama administration officials on whether to send defensive weapons to back Ukrainian forces.
"Where things will end up, we don't know," said the official, who declined to be named because he was not authorised to speak to the media.
I don't think anybody wants to get into a proxy war with Russia... Our objective here is to change the behaviour of Russia.
US Secretary of State John Kerry will travel to Kiev on Thursday for talks with Ukraine's government, the same day NATO defence ministers meet in Brussels.
The policy rethink reflects what US officials say is a frustration with Moscow's continued support for rebels despite months of international economic sanctions, and the collapse of the latest attempt at peace talks at the weekend.
US media reported that Javelin antitank missiles, small arms and ammunition are among weapons Washington may send to Ukraine.
Washington already provides military equipment to Ukraine, such as counter-mortar detection units, body armour, binoculars, small boats and other gear. But it has delayed any decision for months on providing other weapons, from rifles to anti-tank weapons, as it sought a diplomatic solution.
However, Jen Psaki, the State Department spokesperson, said the US was particularly concerned with mounting violence after months of fighting close to the Russian border.
Separatists pounded positions of Ukrainian government troops holding a strategic rail town as both sides mobilised more forces. Five Ukrainian soldiers were killed in clashes at the weekend and 15 civilians died on Saturday.
While the US and western allies pursue a diplomatic solution, the administration is constantly reviewing how to help Ukraine, Psaki said.
"We haven't taken options on or off the table," she said.
The West says the rebels are armed by Russia and supported by several thousand Russian troops, a claim Moscow denies. Both the EU and the US have imposed sanctions against Russia.
"I don't think anybody wants to get into a proxy war with Russia," Psaki said, "Our objective here is to change the behaviour of Russia. That's the reason we have put the sanctions in place."
The developments came as Barack Obama, the US president, prepared to host German Chancellor Angela Merkel at the White House on Monday.
Merkel has said Germany would not supply weapons to Kiev's military but has not objected to Washington doing so.