CBSN

Obama warns N. Korea, Iran on nuke programs

Mr. Obama said the U.S. was also moving forward with Russia to eliminate enough plutonium for about 17,000 nuclear weapons and turn it into electricity. And he heralded an earlier agreement with Russia to reduce nuclear arsenals under the New START Treaty, which Mr. Obama called "the most comprehensive arms control agreement in nearly two decades."

"When we're done, we'll have cut American and Russian deployed nuclear warheads to their lowest levels since the 1950s," he said.

Mr. Obama also prodded Russia in a new way, saying he would seek discussions with Moscow on an unprecedented front: reducing not only strategic nuclear warheads, but also tactical weapons and warheads in reserve. He said he planned to discuss that proposition with former leader Vladimir Putin, who will return to the presidency later this spring after winning an election held earlier this year, when they meet in May.

After his meeting with Medvedev, Mr. Obama said the U.S. and Russia have "more work to do" to bridge their differences, including their approach to violence in Syria. The U.S. has sharply criticized Russia for opposing U.N. Security Council action calling on Syria's president to leave power.

Despite their differences, Medvedev says the relationship between the U.S. and Russia has reached its "best level".