Last month, North Korea got a coveted visit to Pyongyang by a top US official and hinted it was ready to resume negotiations on giving up its nuclear program. Now, the country appears to be backpedaling, raising the bar by demanding an end to international sanctions before any talks. The move sets up a probable new roadblock, because it's highly unlikely the United Nations, the United States and others would roll back sanctions. It also is the latest sign that the punitive measures appear to be taking a toll on the totalitarian regime of Kim Jong Il. The UN Security Council slapped on tough new sanctions last June, strengthening an arms embargo and authorizing ship searches on the high seas, after North Korea carried out a long-range missile launch and its second underground nuclear test. “What is most serious is that the export of weapons has been restricted,” said Yoo Ho-yeol, a professor of North Korean studies at Korea University near Seoul. Military exports are an important source of hard currency for the North, which has long been suspected of selling weapons and missiles to some Middle East countries. The sanctions have likely scared off potential customers, Yoo said. There have been several high-profile weapons seizures or incidents in the past six months. The most recent incident was in December, when a cargo plane that left North Korea with 35 tons of weapons was seized by Thai authorities during a refueling stop in Bangkok. Paperwork seen by arms trafficking researchers indicates the weapons may have been headed to Iran. North Korea lobbied to have the sanctions eased when Stephen Bosworth, the special US envoy to North Korea, visited Pyongyang in December. He responded that wouldn't happen until North Korea returned to the nuclear negotiations and made significant progress in getting rid of its atomic weapons.