The United States and China (search) agree that North Korea must end its nuclear ambitions and resolve the standoff through six-nation talks, Washington's top envoy on the issue said Friday, as efforts to restart the negotiations gained momentum.

Reviving the stalled talks has taken on greater urgency since North Korea's (search) explosive but unconfirmed declaration last week that it has become a nuclear power. The talks involve the two Koreas, the United States, China, Russia (search) and Japan.

North Korea "has made a big mistake in developing these nuclear programs ... and we are to help them overcome this mistake," U.S. envoy Christopher Hill said in Seoul after a visit to Beijing Thursday to meet with Chinese officials.

"But to help them, they are going to have to help themselves, and the first issue they need to do is coming to the table," said Hill, who is also U.S. ambassador to South Korea.

Hill, who was appointed envoy for the nuclear talks on Monday, said he and Chinese officials were in "absolute agreement on the need for North Korea to come back to the process."

China announced Thursday that it would send a top communist party official to North Korea this week, though it did not give an exact date for the trip by Wang Jiarui, head of the party's international department.

Washington hopes China will use its economic influence on North Korea to persuade it to stop developing nuclear weapons. Beijing is North Korea's last key ally and an indispensable supplier of fuel and trade for its impoverished neighbor.

North Korea says it is boycotting the talks until Washington abandons what it calls a hostile policy toward the North.

President Bush on Thursday said diplomacy was the right strategy.

"Now is the time for us to work with friends and allies who have agreed to be part of the process to determine what we're jointly going to do about it," he said at a news conference in Washington.

China has hosted three inconclusive rounds of six-nation talks since 2003. North Korea refused to attend a fourth round, scheduled for last September.

Confronting its own nuclear issues, South Korea on Friday said it will enact a new law to tighten controls over nuclear activities after secret experiments by South Korean scientists embarrassed the country last year.

The Ministry of Science and Technology will complete a draft this month and present a bill to the National Assembly in May, the government said in a statement.

The bill "aims to help prevent nuclear materials from being diverted for use in nuclear weapons or other nuclear explosive devices," the statement said. "It will also outlaw any development of nuclear weapons by the government, groups or individuals and support for such activities."

South Korea is a signatory to international treaties that forbid the development of nuclear weapons. But the country's nuclear activities came under scrutiny last year when it admitted that its scientists conducted plutonium and uranium experiments in 1982 and 2000.

In November, the United Nations' International Atomic Energy Agency criticized the country for the experiments but refrained from taking tougher measures, including referral to the U.N. Security Council.

Although plutonium and enriched uranium are two main elements of nuclear weapons, an IAEA report said there was no evidence that the experiments were applied to an arms program. South Korea has repeatedly said the experiments were unauthorized and were for scientific research only.

But North Korea accused the U.N. nuclear watchdog and the United States of applying "double standards" and giving "tacit approval" to South Korea to pursue a nuclear weapons program.

Also, South Korea said it will begin sending electricity across its heavily armed border with North Korea next month to power a joint-venture industrial park despite heightened nuclear tensions.

The industrial complex in Kaesong, a North Korean town just north of the mine-strewn border, is the best known among the handful of joint economic ventures between the two Koreas.