WASHINGTON — The Bush administration Saturday removed North Korea from its list of countries that sponsor terrorism after North Korea agreed to allow inspectors access to declared nuclear sites, in a deal that drew quick criticism from conservatives.

After weeks of rancorous negotiations, North Korea agreed to resume the disabling of its Yongbyon plutonium plant and permit international inspectors to return.

But although U.S. officials hailed the deal as an important accomplishment, the agreement left unresolved what happens if inspectors seek access to suspicious sites that the regime has not declared. After demanding in negotiations to be given access to other sites, U.S. officials settled for language saying entry to undeclared sites will be granted based on "mutual consent."

The ambiguities of the deal concerned some Republicans, including presidential nominee Sen. John McCain, who said he needed more convincing the deal was a good one. "I expect the administration to explain exactly how this new verification agreement advances American interests and those of our allies before I will be able to support any decision to remove North Korea from the list of state sponsors of terrorism," he said.

His Democratic opponent, Sen. Barack Obama, said President Bush's decision to remove North Korea from the list "is an appropriate response as long as there is a clear understanding that if North Korea failed to follow through, there will be immediate consequences."

"If North Korea refuses to permit robust verification, we should lead all members of the six-party talks in suspending energy assistance, reimposing sanctions that have recently been waived and considering new restrictions," he said.

The administration's position marks a 180-degree turn for a team that came to office in 2001 charging the Clinton administration had been too lenient in its six-year effort to trade North Korea's nuclear program for economic and political benefits. Now the Bush administration counts the program as one of its most important achievements.

Although the denuclearization program has been one of the administration's priorities, it is a complex undertaking that could stretch on for years and meet North Korean resistance at every step of the way. U.S. officials acknowledged in a news conference Saturday that daunting obstacles remain.

"Verifying North Korea's nuclear proliferation will be a serious challenge. This is the most secret and opaque regime in the entire world," said Patricia McNerney, assistant secretary of state for international security and nonproliferation.

The North Koreans have been deeply upset that the United States had not dropped them from the terrorist list as a reward for their limited cooperation to date with the denuclearization program. U.S. officials stressed that North Korea's excision from the list lifts a stigma, but it will have little practical effect because other U.S. laws still impose a number of economic and diplomatic sanctions on the impoverished Stalinist regime.

Officials have been hinting they were near a deal for several days, but they had to deal with last-minute resistance from the Japanese, who had reservations about removing North Korea from the terrorism list before they had addressed Japanese concerns about North Korea's abductions of Japanese citizens.

President Bush called Japanese Prime Minister Taro Aso on Saturday morning. In a statement, the White House said the United States "will continue to strongly support Japan's position on the abduction issue and will urge North Korea to take immediate steps to implement the commitments (it has made on the issue)."