While Kim's movements are shrouded in secrecy, diplomats cited by South Korean media said he met military chief Jiang Zemin and Premier Wen Jiabao.
The reclusive leader arrived in Beijing by train Monday on an unannounced visit accompanied by a 30- to 40-strong entourage, and headed straight into talks with President Hu Jintao.
Reports said Kim told Hu he was ready to give up his country's nuclear programs if the United States changed its "hostile attitude".
In meetings Tuesday, he reiterated that while he wanted a peaceful end to the standoff, Washington must first compensate the Stalinist state before any climbdown on its nuclear facilities, Yonhap news agency said.
On Monday, Hu reportedly briefed Kim on Washington's position -- the complete, verifiable and irreversible dismantling of North Korea's nuclear programs before any aid is offered -- following his meeting last week in China with US Vice President Dick Cheney.
He also "indirectly" advised Kim to soften his hardline stance toward the United States, the Munwha Ilbo newspaper said.
Cheney upped the stakes by saying time was running out to resolve the standoff, presenting China with new intelligence that North Korea has nuclear bombs.
During his meeting with Kim, Wen was expected to offer food and energy assistance and ways of linking Pyongyang's economic development program with those being pushed by China's northeastern provinces bordering North Korea.
Yonhap said Kim had shown keen interest in China's economic growth during his visit and discussed ways of strengthening economic ties with Wen.
He will reportedly visit the cities of Shenyang or Dalian on his way back to North Korea to witness for himself the way they are being transformed into hubs of economic development.
With its economic reforms failing, North Korea is desperate for aid from China, one of its only allies, as well as ideas on how to imitate its neighbour's vibrant growth.
"North Korea is presently under an enormous amount of economic difficulty," Dong-bok Lee, a former South Korean politician who was a pioneer in improving North-South Korean relations, told AFP.
"There has been much talk about its reform measures but they resulted in total failure.
"Its economy is worse than it was two years ago and this is crucial to the survival of the regime. It is also entering a sensitive era because of the changing nature of the nuclear crisis."
Finding a solution to the nuclear issue is widely seen as the key to unlocking outside aid to help the economy and ensure the regime's existence.
Fuel shipments were cut by the US, Japan, South Korea and the European Union in late 2002 after US envoy James Kelly said Pyongyang had admitted it was trying to build nuclear weapons.
"China will respond to North Korea's demands. They don't want to push the government over the edge, they recognise this could result in an explosion, literally," said Paul Harris, a north Asian expert at Hong Kong's Lingnan University.
China and North Korea have refused to publicly announce Kim's presence in Beijing, despite Washington confirming he was in the Chinese capital.
On earlier Kim visits to China, Beijing refrained from announcing the trip until it was over, apparently out of security considerations for Kim.
China has been hosting six-nation talks to resolve the nuclear standoff, which also bring together the two Koreas, the United States, Russia and Japan.
A new round of talks is scheduled to take place before the end of June and China Tuesday expressed confidence that they would go ahead as planned.
"We should have the confidence that the third round of the six-party talks shall be held before the end of June ...," said foreign ministry spokesman Kong Quan.