The U.S. ambassador to the United Nations says the sanctions placed on North Korea by the U.N. are putting pressure on the country to halt its nuclear program.

Susan Rice told the Associated Press on Tuesday that North Korea has indicated in a variety of ways that it is feeling the pressure of sanctions and that it may be responding accordingly.

She added that U.S. special envoy Stephen Bosworth's visit to Pyongyang was not to open bilateral negotiations between the U.S. and North Korea but to very clearly convey that President Barack Obama expects the North to return to the six-party nuclear talks.

Upon his return from the meetings in Pyongyang, Bosworth said the North had even lobbied to have the sanctions eased.

South Korean Foreign Minister Yu Myung-hwan said in a regular news briefing last week that North Korea told Bosworth the U.N. sanctions were unfair.