A Chinese delegation including the country's top nuclear envoy pledged friendship and deeper ties during a visit to North Korea on Monday as Beijing sought to push its communist ally back into nuclear disarmament talks amid outrage over its missile tests.

Vice Foreign Minister Wu Dawei, China's main nuclear negotiator, arrived in Pyongyang as part of a goodwill delegation led by Vice Premier Hui Liangyu to celebrate the 45th anniversary of a friendship treaty between the neighbors.

The group, who will stay for six days, exchanged congratulatory messages with North Korean officials, the official Xinhua News Agency said. The Chinese message was addressed to the North's leader Kim Jong Il from President Hu Jintao, Premier Wen Jiabao and Wu Bangguo, the top legislator, Xinhua said.

A North Korean delegation was also expected in China on Tuesday to mark the treaty anniversary.

"Leaders of the two sides agreed that to consolidate and develop the China-DPRK friendship has been the firm stand of the two governments and two parties," Xinhua said, using the initials for the North's official name, the Democratic People's Republic of Korea.

"The two countries will further increase exchanges, strengthen cooperation and push forward the bilateral friendly cooperative ties," Xinhua said, citing the messages.

CountryWatch: North Korea

China is the North's biggest source of aid and the two sides have regular contacts. While Beijing has been under pressure to use its influence to persuade the regime to return to disarmament talks, it is unclear how much sway Beijing actually holds over the North.

The Chinese government hasn't said whether Wu or Hui would bring up the six-nation nuclear talks during their trip or released details on who they will meet. But a ministry spokeswoman has said China was "making assiduous efforts" in pushing for a resumption of the negotiations.

Talks have been deadlocked since November because of a boycott by Pyongyang in protest of a crackdown by Washington on the regime's alleged money-laundering and other financial crimes.

China has suggested an informal gathering of the six nations, which could allow the North to technically stand by its boycott, but at the same time meet with the other five parties — South Korea, China, the U.S., Japan and Russia.