This is the third one of its kind since they arrived in Beijing for the fourth round of the six-party talks which aim to solve the Korean Peninsula nuclear issue.

Experts say that the unusually high-frequency of "one-on-one" meetings between the two leading roles of the issue shows that the US-DPRK bilateral discussions have come to a "substantial" phase.

"If we can say that in the former two meetings the two sides had put out their attitudes and differences, then in this meeting,they should begin a consultation of how to solve their differences," said Jin Canrong, a professor on international politics with the People's University of China.

"This means that the talks have come to a substantial phase," Jin said.

Compared with the former three rounds of talks held in Beijing in 2003 and 2004, both the DPRK and the US delegation have shown strong willing of communication in this round of talks.

On July 25, a day before the talks was opened, the two sides met for 75 minutes unexpectedly. On July 26, they met for the second time, which was described as "long," "good," and "businesslike" by US government officials.

Today's consultation lasted for about three hours.

On the definition of "denuclearization," the DPRK side insisted that the US side should clear up its nuclear threats to the DPRK,including its "nuclear umbrella" for the Republic of Korea, a legacy of the 1950-53 Korean War.

The DPRK is not "fully satisfied" with the proposal that the United States made in June 2004 and worries about who should take the first step. It is also afraid that the DPRK has taken on too much obligation while the other parties will not carry corresponding measures.

While the US side put out its last year's proposal again, it admitted that the two sides still have differences, that is, who should take action first. But the US said the two sides have reached consensus on the definition of "denuclearization."

Christopher Hill, head of the US delegation, said Thursday afternoon, "We had a lengthy discussion and I must say there are a number of differences."

"On the other hand, on some points we have some common understanding on how to proceed," he said. But there were details about this. "This morning's meeting should focus on the definition of denuclearization and who should take action first," said Fu Mengzi, director of the Institute of American studies under the Chinese Academy of Contemporary International Relations.

He said though the two sides have shown flexibility, the distrust between the two sides lasted long and it is not sure that they can make progress on reducing the differences.

"Probably the two parties have affirmed the consensus that they had reached in order to write them on a joint document that might come out at the conclusion of the talks," said Jin Linbo, head of the Asia-Pacific Office under the China Research Institute of International Studies.

"It should include the United States' recognition of the DPRK as a nation with sovereignty, and the US has no intention to attack the DPRK, and the DPRK's goal to realize a nuclear-weapon free peninsular," he said.

Other delegations of the six-party talks also attached great importance to the "one-on-one" meetings between the DPRK and the United States.

Japan's chief delegate, Kenichiro Sasae, said their talks would determine the course of the following negotiations.

Without progress made between the US and the DPRK, there won't be an agreement on a joint statement from all sides at the conclusion of the talks, he said.

Russian delegation head Alexander Alexeyev said the meeting between the DPRK and the United States may influence the result of the six-party talks to a large extent.

US government official said on Tuesday afternoon the two sides will hold a fourth meeting Friday.

Qin Gang, spokesman of Chinese delegation, said the the fact that the DPRK and the US continued their meetings marks a progress and also a most important fruit of this round of talks.

The fourth round of the six-party talks moved into the third day Thursday.There is still no information to indicate how long the ongoing talks will last.