U.S. President Barack Obama says the United States on September 12 will strengthen sanctions in the defense, finance and energy sectors to punish Russia over its "illegal actions" in Ukraine.
The move was coordinated with the European Union, which said a new round of sanctions on Russia would go into effect on September 12.
Obama said in a statement the move would worsen the Kremlin's deepening political and economic isolation.
Obama said, "We are implementing these new measures in light of Russia's actions to further destabilize Ukraine over the last month, including through the presence of heavily armed Russian forces in eastern Ukraine."
He added that Washington was closely watching the implementation of a cease-fire deal agreed between Moscow and Ukraine, but had "yet to see conclusive evidence that Russia has ceased its efforts to destabilize Ukraine."
Obama said that his administration would lay out the details of the new sanctions on September 12 but added that they would exact costs on those close to Russian President Vladimir Putin.
The president also offered Moscow a choice. He said, "If Russia fully implements its commitments, these sanctions can be rolled back."
But he added, "If, instead, Russia continues its aggressive actions and violations of international law, the costs will continue to rise."
In Brussels, European Council President Herman Van Rompuy also said the new EU sanctions could be scaled back or repealed.
Van Rompuy said the EU would monitor the peace process in eastern Ukraine to determine before the end of September if changes are merited.
The fresh sanctions tighten restrictions on weapons deals with Russian defense firms. They also include a ban on financing from EU countries to Russian energy firms like Rosneft, Transneft, and Gazprom Neft.
New Ruble Low
It also add the names of 24 Russian citizens and pro-Russian separatists in eastern Ukraine to the existing sanctions list, targetting them with travel bans and freezing their assets in the EU.
Meanwhile, the Russian ruble fell to a new record low of 37.57 to the dollar.
Russia’s Foreign Ministry on September 11 accused the EU of undermining peace efforts in Ukaine, saying that by imposing more sanctions, "the EU has practically decided against the process of a peaceful settlement."
It also called the sanctions an “unfriendly act” and warned Moscow's retaliation would be "absolutely proportionate."
Andrei Belousov, and aide to Russian President Vladimir Putin, said Russia has already compiled a list of consumer goods that it will ban from being imported into Russia in response to the EU's sanctions.
The measures were agreed by EU leaders on the sidelines of a NATO summit on September 5 and formally approved in Brussels on September 8.
But publication of the decision was delayed to allow time to assess the implementation of a cease-fire agreement in eastern Ukraine between Kyiv and pro-Russian separatists.
The EU previously has said that sanctions could be suspended if Moscow honors the conditions of the cease-fire and pulls its troops out of Ukrainian territory.
Russia denies accusations by the EU, Kyiv, and NATO that it has sent Russian soldiers and weapons to reinforce separatists who are fighting government forces in eastern Ukraine’s Donetsk and Luhansk provinces.
Ukrainian President Petro Poroshenko said on September 10 that Russia had withdrawn 70 percent of the troops Kyiv claims were sent into eastern Ukraine, giving hope to peace initiatives proposed along with the shaky cease-fire.
But a NATO official on September 11 said Russia still has at least 1,000 soldiers in eastern Ukraine.
With reporting by Reuters, AP, AFP, dpa, and RFE/RL's Moldovan Service