The United States is approaching talks on North Korea's nuclear program with a spirit of flexibility but is demanding that the communist government prove it will stop developing nuclear weapons, Secretary of State Colin Powell (search) said Monday.

With preliminary talks under way in Beijing, and formal negotiations due to open Wednesday, Powell said, "We will enter these talks as we have entered previous talks: with flexibility and with an attitude of trying to resolve this problem."

Powell was responding to persistent reports that China and South Korea were urging the Bush administration to ease its tough line and accept a step-by-step compensation program to entice North Korea (search) to start a phased-in process of ending its nuclear program.

"We are not prepared to compensate North Korea somehow for not doing something that they never should have done to begin with," State Department spokesman Richard Boucher said.

The four countries aligned with the United States in the talks -- China, Japan, South Korea and Russia -- share the goal of denuclearizing the Korean peninsula, Boucher said.

President Bush has indicated he is willing to negotiate with the other countries on ways to guarantee "that the North Koreans don't have to worry about their security," Boucher said.

Also, Boucher said, other nations participating alongside the United States have indicated that if the negotiations should move toward a complete and irreversible dismantling of North Korea's nuclear weapons program, they would be prepared to offer "economic benefits and other ties to North Korea."

The United States has provided food to North Korea over the years but otherwise has steered clear of assisting its troubled economy. In return for a freeze of a plutonium-based nuclear program in 1993, however, the former Clinton administration promised 500 metric tons of heavy oil annually. Japan and South Korea helped with energy, as well.

The assistance was halted after discovery of a secret North Korean uranium-based nuclear weapons program (search) in 2002.

The current six-nation talks have made little headway since they began last August. At the same time, North Korea's leader, Kim Jong Il (search), has visited China, and met with Japanese Prime Minister Junichiro Koizumi (search) in Pyongyang, North Korea's capital. North Korea also has held high-level military talks with South Korea.

Powell spoke to reporters after meeting with Mohamed ElBaradei, director general of the International Atomic Energy Agency (search).

Powell did not say explicitly what he meant that the United States would show a "spirit of flexibility," but he might have been referring to the prospect of security talks with North Korea.

"The other members of the six-party talks have indicated a willingness to provide some assistance rather quickly" if negotiations were productive, Powell said.

As for the United States, Powell said, it "will want to see performance on the part of the North Koreans."

"They should stop doing what they are doing," Powell said about a program that U.S. intelligence agencies are convinced poses a nuclear weapons threat.

Powell said he had briefed ElBaradei about the talks with North Korea.

ElBaradei, in a brief statement, said, "The earlier we are in a position to resolve the North Korean issue, which I find one of the most dangerous challenges facing the international community, the better."