The United States suspended all military engagements with Russia, including military exercises and port visits, as Washington sought ways to punish Moscow over its military intervention in Ukraine without escalating the crisis.

The announcement made on Monday from the Pentagon came hours after President Barack Obama warned the U.S. government will look at a series of economic and diplomatic sanctions that would isolate Moscow, Reuters reported.

The United States also put trade and investment talks with Russia on hold.

“We call on Russia to de-escalate the crisis in Ukraine and for Russian Forces in Crimea to return to their bases,” Pentagon spokesman Rear Admiral John Kirby said in a statement.

Also on Monday, U.S. President Barack Obama said that Russia violated international law by militarily intervening in Ukraine.

Obama told reporters that Russian President Vladimir Putin needs to allow international monitors to mediate a deal in Ukraine acceptable to all Ukrainian people, according to Reuters.

The U.S. is weighing its response to Russia’s so far bloodless incursion into Crimea. Despite an international outcry, Putin has shown little sign of backing down, and Russia has built up armored vehicle presence near Crimea and staged military maneuvers in what appears to be a show of strength.

“Over time this will be a costly proposition for Russia. And now is the time for them to consider whether they can serve their interests in a way that resorts to diplomacy as opposed to force,” Obama said.

U.S. Secretary of State John Kerry is expected to propose ways in which a negotiation between Russia and Ukraine could be overseen by a multilateral organization when he goes to Kiev on Tuesday, Obama said.

Kerry will also offer an economic aid package for Ukraine, the American President added.

Source: Reuters