Breaking a 13-month deadlock, diplomats from six nations opened a new round of negotiations Tuesday designed to persuade North Korea to dismantle its nuclear weapons program.

Delegation chiefs from the United States and North Korea laid out their positions using what seemed to be particularly conciliatory language during a round of preliminary speeches, with each seeking to appear receptive to the other's key demands. Despite these gestures, diplomats cautioned that long, difficult negotiations lie ahead.

North Korean Vice Foreign Minister Kim Kye Gwan, who leads his country's negotiating team, reiterated his government's declared willingness to work for a nuclear-free Korean Peninsula -- the Bush administration's main goal and the overall purpose of the six-party process that has been underway under China's aegis since August 2003.

"The fundamental thing is to make real progress in bringing about denuclearization of the Korean Peninsula," Kim said in an opening session broadcast live on Chinese state television. "This requires a very firm political will and a strategic decision by the parties that have an interest in ending the threat of nuclear war. The North Korean government is fully prepared for these talks, and our understanding is that the United States and the other countries are also ready."

Christopher Hill, assistant secretary of state for East Asian and Pacific affairs and head of the U.S. team, declared that, although the Bush administration has weighed other options, the United States remains committed to the six-party talks as the best way to peacefully resolve the standoff. But the talks are at a "critical juncture," he added, underlining the need for progress to show the world -- and particularly skeptical officials in the Bush administration -- that the process is worthwhile.

"We view DPRK sovereignty as a matter of fact," he added, going out of his way to respond to key demands put forward by North Korea, formally known as the Democratic People's Republic of Korea. "The United States has absolutely no intention of invading or attacking the DPRK and remains prepared to speak with the DPRK bilaterally in the context of the six-party talks."

The new round of talks -- which also involve representatives of South Korea, Japan, Russia and China -- are the first since June 2004 and are aimed at producing enough progress to justify continuing the process, a senior U.S. official said. To make that possible, he added, diplomats plan to stay in Beijing for as long as necessary, seeking relatively easy points of agreement that would become a platform for further talks.

The open-ended attempt to build a list of issues the sides agree on marked a shift in tactics from the three previous rounds of negotiations. But ultimately, the U.S. official said, the goal has been the same since the talks began in August 2003: persuading North Korea to dismantle its nuclear weapons program in exchange for aid and recognition from the United States and its allies.

Senior U.S. and North Korean diplomats sat down Monday for what were described as "businesslike" bilateral discussions. Those talks included direct, senior-level contact between the two hostile governments, a relatively rare occurrence. The discussions, which officials described as informal, suggested a softening of the previous U.S. effort to play down bilateral contacts and to emphasize that all six nations must be involved in any negotiations.