MOSCOW (Reuters) - Russia said on Thursday the United States would violate international agreements and destabilize the situation if it supplies weapons to Ukrainian forces fighting separatists in the country's east.
A U.S. official suggested on Wednesday that Washington should consider providing weapons to Ukraine.
Russian Foreign Ministry spokesman Alexander Lukashevich said that sent a "very serious signal".
"If there is a change of policy (of providing only non-lethal assistance to Ukraine), then we can speak of a serious destabilizing factor that can seriously impact the balance of forces in this region," Lukashevich told a news conference.
Lukashevich was addressing reporters before a visit to Ukraine by U.S. Vice-President Joe Biden, who was due to arrive in Kiev on Thursday evening.
Lukashevich cautioned against "a major change in policy of the (U.S.) administration in regard to the conflict" in Ukraine.
"That (would be) a direct violation of agreements reached, including (agreements reached) with the participation of the United States," he said.
Washington backs Kiev in its struggle against the pro-Russian separatists in two eastern regions of Ukraine and has imposed sanctions on Russia over its policies in the crisis.
Moscow supports the separatists but denies it is part of the armed conflict which the United Nations says has killed more than 4,300 people since mid-April.
(Reporting by Thomas Grove, Writing by Gabriela Baczynska, Editing by Timothy heritage)