U.S. and North Korean diplomats failed to reach an agreement Wednesday on when to resume six-nation talks on Pyongyang's disputed nuclear program, but stressed their commitment to moving the process forward.

U.S. Assistant Secretary of State Christopher Hill said after two days of talks with North Korean Vice Foreign Minister Kim Kye Gwan that the sides "shared ideas that could help ensure progress when the six-party talks resume," according to a U.S. Embassy statement.

The North said in its own statement that it "promised to study these ideas."

No date was set for the talks to resume. Hill planned to leave Beijing on Thursday without a follow-up meeting, said Susan Stevenson, spokeswoman for the U.S. Embassy in Beijing.

Hill and Kim also met with Chinese Vice Foreign Minister Wu Dawei during the talks Tuesday and Wednesday. The Chinese Foreign Ministry said in a statement on its Web site late that the parties "frankly and deeply exchanged views on the issue of promoting the process of the six-party talks and improve mutual understanding," without elaborating.

"The three parties also agreed to strive for the progress of the talks," the statement said.

Japan's Kyodo News agency cited unidentified officials at the talks as saying Kim had demanded the U.S. lift financial sanctions and freeze U.N. sanctions that were imposed after the October nuclear test.

Hill responded by saying that the possible lifting of financial sanctions can be discussed during the talks and working-level discussions, which are expected to be held simultaneously, Kyodo said. Similar stances were taken when the three met bilaterally and trilaterally on Tuesday, Japanese and South Korean media have reported.

North Korea agreed in September 2005 to abandon its nuclear program in exchange for security guarantees and aid. But Washington imposed the financial sanctions against a Macau-based bank on suspicions it was laundering counterfeit money for the North Koreans. Angered by the move, Pyongyang withdrew from the talks two months later.

The six-party talks involve the United States, North Korea, Japan, South Korea and Russia, which has not sent an envoy to Beijing.

State Department spokesman Sean McCormack said in Washington that the main goal of the Beijing meetings was to "make sure that everybody, at least, has a good, solid understanding of what might happen" when the six-nation talks resume.

Japanese Prime Minister Shinzo Abe said in Tokyo that just resuming the talks was not the main objective. "Our efforts are aimed at holding six-party talks that produce results," he said.

Kim's trip to Beijing — a rare overseas visit for a North Korean official — and the presence of other negotiators had lifted expectations that there could be a breakthrough in ongoing efforts to restart the talks.

An unannounced meeting between Hill and Kim last month in Beijing led to Pyongyang agreeing to return to the arms negotiations amid heightened tensions after the Oct. 9 nuclear test.

Meanwhile, a South Korean lawmaker said Wednesday he believed the North was making preparations to possibly conduct a second nuclear test next month or early next year unless the U.S. offers economic concessions, such as lifting financial restrictions against Pyongyang.

"I believe that there are specific movements in North Korea to prepare for a second nuclear test," lawmaker Chung Hyung-keun said, citing intelligence obtained by state intelligence agencies, according to Chung's office. He did not elaborate.

There had been speculation that Pyongyang was preparing for a second test after it conducted its first nuclear explosion Oct. 9. Last month, however, South Korean media reported that the U.S. military had not detected any signs of preparations for a second test.