SEOUL, South Korea -- North Korea has warned it may scrap a moratorium on its nuclear program and long-range missile tests if the Bush administration continues its "hard line" policy.

A statement from the country's foreign ministry Thursday said Washington was attaching unacceptable conditions by demanding the North disarm before agreeing to develop relations.

The angry statement referred to comments by senior Bush administration officials that they would review policy toward the communist country and that they expected reciprocity from Pyongyang.

Koreans on both sides of the Demilitarized Zone interpreted those remarks as an indication that Washington might take a tougher approach toward Pyongyang in the wake of improved U.S.-North Korean ties under former President Bill Clinton.

North Korea agreed to suspend missile tests in September 1999 while talks continued with Washington on resolving concerns over Pyongyang's missile program.

In turn, the United States eased some sanctions.

"We promised not to test-fire long-range missiles during the duration of talks on the missile issue, but we cannot do so indefinitely," the North said in a statement.

"The new U.S. foreign and security team is making a fuss by saying that it will take a hardline stance on us," the ministry said.

"But this is an attempt to reverse the past course of conciliatory and cooperative relations between us and the United States, and break our will with force."

Nuclear reactors behind schedule

North Korea also said it was unhappy with the slow progress of the construction of two nuclear power plants being built in the communist country under a 1994 agreement with the United States.

The two reactors, originally scheduled to be completed by 2003, are several years behind schedule.

After talks in Geneva in 1994, the North agreed to halt and eventually dismantle its nuclear program, which Western nations feared was aimed at trying to develop nuclear weapons.

In exchange, the United States, Japan and South Korea agreed to build two light-water nuclear reactors in North Korea and provide interim supplies of fuel oil to keep North Korea's ailing industries going.

South Korea and Japan are financial contributors to the U.S.-led program.

"If the United States continues to fail to honor the agreement, we don't feel that we should cling to it," the North said.

An official at South Korea's unification ministry said it was the first time North Korea's foreign ministry had made such an official statement against the Bush administration.

However, he said the position itself was not out of character with the North's stance so far.

Steps toward reunification

Relations between the two Koreas have improved dramatically since the South's President Kim Dae-jung traveled in June to Pyongyang for an unprecedented summit with leader Kim Jong Il.

The two sides have stopped border propaganda broadcasts, are now working on the reconnection of a cross-border railway, and have held two temporary reunions of separated family members.

A third round of reunions is scheduled for Feb. 26-28.

On Thursday a delegation of South Korean officials arrived in Pyongyang for talks on cooperation in flood control efforts along the Imjin River, which crosses the border between the two countries, the North's media reported.

Washington, which backed the South against the North in the 1950-53 Korean War, has been a firm supporter of Seoul's policy of trying to engage the North in order to reduce tension on the divided peninsula.

Washington's approach is not expected to change in any fundamental way as long as it perceives that Pyongyang is responding with concrete gestures of reconciliation.

Kim Dae-jung plans to meet President Bush in Washington on March 7 to discuss North Korea policy.

North Korea is still listed by the U.S. State Department as a sponsor of terrorism, a label that prohibits virtually all but humanitarian aid to Pyongyang.

CNN Seoul Bureau Chief Sohn Jie-Ae and The Associated Press contributed to this report.