Russia says there will be repercussions if Washington imposes new sanctions on Moscow over the Ukraine crisis.
Deputy Foreign Secretary Sergei Ryabkov on Saturday blamed "anti-Russian moods" in Washington for the new bill authorizing lethal military aid to Kyiv and deeper sanctions against Russia.
The Russian Foreign Ministry said in a statement Friday the legislation, known as the Ukraine Freedom Support Act, had an "openly confrontational nature" and amounted to "blackmail."
The ministry said the bill will cause "deep regret" and destroy chances for any joint efforts to end the Ukraine crisis.
Russian Foreign Minister Sergei Lavrov is expected to discuss the matter with U.S. Secretary of State John Kerry when they meet Monday in Rome.
The bill, passed unanimously by the U.S. Senate, authorizes $350 million in military hardware and munitions to Ukraine, and new sanctions against high-profile Russian exporters. The bill now heads to the House of Representatives.
Kyiv and Western governments accuse Moscow of supplying direct aid to pro-Russian rebels seeking autonomy in Ukraine's east. The Kremlin has repeatedly denied the charges and says that Russian soldiers seen fighting alongside rebels are doing so as volunteers.
As the latest political drama played out in Washington and Moscow, Ukraine's President Petro Poroshenko said a fragile cease-fire between government forces and Russia-backed rebels appeared to be holding.
Poroshenko, speaking early Friday, said 24 hours had passed without any deaths or injuries in Ukraine's war-torn east.
The Ukrainian leader pleaded with Russia Friday to close its border with Ukraine, saying there would be "peace and stability" in his country within weeks if Moscow did so.
In another development Friday, Voice of America's Ukrainian Service celebrated its 65th anniversary. Diplomats, human rights experts, representatives of the Ukrainian-American community, as well as past and present members of the Ukrainian Service joined VOA Director David Ensor in the celebrations.