Deputy Secretary of State Richard Armitage said at a news conference in Canberra he would not speculate about how much the talks will achieve.
"We're having the talks, we'll do our best, we'll be businesslike, we'll be serious and sincere," he said. "Beyond that I'm not going to make any speculation, it would be foolhardy."
But Armitage said the top American arms control official, U.S. Undersecretary of State John Bolton, would not participate.
North Korea's official news agency has reported Pyongyang won't accept him as a negotiator in the talks, and called him "human scum" after he criticized North Korean leader Kim Jong Il.
Still, Armitage repeated earlier U.S. statements that Washington, not Pyongyang, will choose its delegation for the talks.
The talks are aimed at resolving tensions over U.S. complaints that Pyongyang is trying to develop nuclear weapons in violation of a 1994 agreement. According to U.S. officials, the North has proposed giving up its nuclear programs in return for a security guarantee and economic aid from Washington.
Armitage told the Australian Broadcasting Corp. television that the talks would be "probably starting around the 27th of this month in Beijing."
Pyongyang agreed to the six-way meeting after saying for months that it would only consent to bilateral talks with the United States. The North says it will work on the sidelines of the negotiations to push for one-on-one talks with Washington, which has insisted on multilateral talks because it says the North's nuclear program is a regional concern.
The nuclear standoff began in October, when U.S. officials said North Korea acknowledged having a uranium-based nuclear weapons program. That led the United States to cut off fuel shipments to North Korea that had operated under a 1994 deal halting the North's nuclear development.
Pyongyang subsequently threw out international inspectors and vowed to begin reprocessing spent fuel rods into bomb-making plutonium. In a series of public boasts and private statements to envoys in the ensuing months, North Korea has said that it has nearly completed that reprocessing, although U.S. intelligence could not confirm it.
The last time the United States and North Korea had official talks was in April in Beijing. U.S. officials said that North Korea claimed at the talks it already had nuclear bombs and planned to build more.
U.S. officials believe North Korea already has one or two nuclear bombs and can yield enough plutonium from its 8,000 spent nuclear fuel rods to build several more within months. There are also indications the North is preparing for some kind of nuclear test.
In his speech last month, Bolton criticized the Security Council, saying its credibility was at stake because it had failed to take up the North Korean nuclear issue.
According to press accounts, Bolton also said in his speech that, while North Korean leader Kim lived in luxury, "hundreds of thousands of his people locked in prison camps with millions more mired in abject poverty, scrounging the ground for food. For many in North Korea, life is a hellish nightmare."
In the past, Bolton has clashed with intelligence officials over his characterizations of alleged weapons of mass destruction in other countries.
Last month, The New York Times reported that the CIA had blocked Bolton from telling Congress that Syria's biological and chemical weapons programs were a danger to the region. The intelligence agency disagreed with the assessment.
In June, an intelligence analyst, Christian Westermann of the State Department's Bureau of Intelligence and Research, told the Senate Intelligence Committee that he had felt pressure from Bolton after the two disagreed over whether Cuba had a biological weapons program.
Bolton said last year that the U.S. believed Cuba had such a program.