Updated

U.S. and North Korean envoys held their fourth one-on-one meeting this week Friday as six-nation talks aimed at persuading Pyongyang (search) to abandon its nuclear weapons program stretched into the longest such negotiations since the process began in 2003.

U.S. Assistant Secretary of State Christopher Hill (search) began a one-on-one meeting with North Korean Vice Foreign Minister Kim Kye Gwan at the state guesthouse where the talks are taking place, China's official Xinhua News Agency reported.

No deadline has been set for the nuclear talks in the Chinese capital to wrap up, unlike other sessions that lasted about three days.

Earlier talks produced no breakthroughs, and many delegates said they didn't expect any in this round, which convened after a 13-month hiatus during which the North refused to participate, citing "hostile" U.S. policies. Most parties have said they hope merely to set a date for a fifth session.

Despite the meetings with the North Koreans, the United States ruled out negotiating a bilateral agreement.

"That approach was tried and it failed," White House press secretary Scott McClellan said Thursday, referring to a 1994 pact that collapsed after U.S. officials accused North Korea (search) of running a secret uranium enrichment program in late 2002. The North later pulled out of the Nuclear Nonproliferation Treaty and restarted its main nuclear reactor, spawning the current crisis.

Hill said earlier that he hoped to start drafting a statement by the end of Friday with results of the talks so far — a possible indication that negotiations were inching forward. American officials have said the document would contain "agreed principles" for future negotiations.

"We've had a lot of discussions with a lot of the delegations, so we'd like to see if we can put some of these thoughts down on paper and see where we are," Hill said Thursday. "We have a long way to go still."

The six-nation talks that began Tuesday are the fourth round in which China, Japan, Russia, South Korea and the United States have come together to press North Korea to give up its nuclear ambitions.

Most of the negotiations between the United States and North Korea have lasted for three days or less — Aug. 27-29, 2003; Feb. 25-28, 2004, and June 23-26, 2004 — but in 1994, United States and North Korea held several weeks of nuclear negotiations.

Thursday's bilateral meeting — held as part of six-nation talks — was "maybe the first time both sides talked so deeply, so concretely and for such a long time," said Deputy Foreign Minister Alexander Alexeyev, the chief Russian delegate.

The increased contacts at this round between North Korea and the United States — who remain technically at war with some 32,500 U.S. troops based in South Korea — have raised hopes for movement in the nuclear crisis that began in late 2002, after the U.S. accused the North of running a secret uranium enrichment program.

However, Secretary of State Condoleezza Rice, interviewed on PBS' NewsHour with Jim Lehrer, said any agreement in which North Korea gave up its nuclear weapons "is really only going to be achieved in a six-party framework."

Rice said "breakout sessions in which people talk directly" are not unusual in negotiations involving several countries.

Hill was representing Washington for the first time at the talks, and his contacts with the North Koreans were a departure from previous meetings. An experienced negotiator who previously has focused mostly on Eastern Europe, Hill has worked on resolving conflicts in Bosnia and Kosovo.

Meanwhile, a news report said North Korea hasn't assembled a working nuclear bomb but that the country has acquired all the components necessary to build one.

The North claimed to have nuclear weapons in February. However, a diplomatic source close to the arms talks told Russia's Interfax news agency that Pyongyang informed China that its announcement meant the North was able to build a detonator, the last component it needed for a bomb.

North Korea has avoided spending to build up a nuclear stockpile, but the source told Interfax that the country would begin to do so in the face of unacceptable demands or a lack of security guarantees from the United States and its allies.

Earlier at the talks, North Korea called for the U.S. to remove its alleged nuclear threat against the communist nation. It also reportedly said Washington must abandon plans for toppling the communist regime and set up mechanisms for peaceful relations before it hands over its atomic weapons.

The United States repeatedly has said it has no intention to attack North Korea, and stuck by its offer of security guarantees and aid only after the North is certified as free of nuclear weapons by international inspectors who can ensure that the country stays that way.

The North has said that's too much to ask for without getting any aid in return.

The nuclear standoff hasn't dimmed relations between the two Koreas, and the foreign ministers from the North and South met Thursday at an Asian conference in Laos where they agreed to work together in the international arena.

South Korean Foreign Minister Ban Ki-moon also proposed having regular meetings with his North Korean counterpart Paik Nam Sun, who didn't directly respond to the suggestion.