Russia on Thursday warned the United States against sending weapons to Ukraine, saying such action would cause "colossal damage" to ties between the former Cold War foes.
Moscow is "seriously concerned" by discussions in the West about possible arms supplies to Ukraine which is battling a pro-Kremlin insurgency, said foreign ministry spokesman Alexander Lukashevich.
"Without a doubt, if such a decision is realised, it will cause colossal damage to US-Russian relations, especially if the residents of Donbass (Donetsk and Lugansk regions) start to be killed by American weapons," Lukashevich said.
"This would not only threaten to escalate the situation in the southeast of Ukraine, but threatens the security of Russia, whose territory has been repeatedly shelled from Ukraine."
The West has repeatedly accused Moscow of fuelling the insurgency in eastern Ukraine -- where more than 5,000 people have been killed since last April -- with weapons and regular army units, but Russia denies any involvement.