North Korea may be preparing for its third nuclear test as the United Nations considers new sanctions on the regime, according to a U.S. government official.

The official, who spoke on condition of anonymity because he was not authorized to discuss the information publicly, said that there are indications that North Korea may be readying for another nuclear test.

North Korea conducted an underground explosion on May 25, the second time since a 2006 nuclear test.

A draft U.N. resolution proposed Wednesday would impose tough sanctions on North Korea's weapons exports and financial dealings, and allow inspections of suspect cargo in ports and on the high seas.

North Korea has threatened to retaliate if new sanctions are adopted.

President Barack Obama's special envoy on North Korea, Stephen Bosworth, said Thursday that the United States is determined to make sure the North faces serious consequences for its growing missile and nuclear threat.

Bosworth told lawmakers at a hearing that the Obama administration is considering freezing North Korean accounts at banks outside the country.

Also on Thursday, CIA Director Leon Panetta said that U.S. intelligence agencies are watching North Korea very closely in hopes of detecting or preventing North Korea's sale of nuclear and missile expertise and technology to anyone willing to pay.

North Korea is a hard target to spy on but we are making good progress, Panetta said.