North Korea's leader Kim Jong-Il was reportedly in Beijing on Wednesday ahead of summit talks with Chinese President Hu Jintao, on his first trip abroad in years to secure much-needed economic aid.

The 68-year-old Kim, who arrived in China on Monday, is expected to offer Beijing reassurances that Pyongyang will return to nuclear disarmament talks it abandoned more than a year ago, in exchange for economic aid and investment.

North Korea is under tough UN sanctions over its refusal to halt its atomic drive, and its economy suffered a new blow last November when a currency reform backfired, wiping out people's savings and sending prices soaring.

China is Pyongyang's sole major ally and its main source of finance, food and fuel. It is also seen as the only country with any ability to put pressure on Kim's hardline regime.

Kim arrived in Beijing on Wednesday for talks with Hu after apparently visiting the port city of Tianjin southeast of the Chinese capital, South Korea's Yonhap news agency said, citing unnamed sources.

An AFP photographer saw a convoy of cars believed to be carrying Kim entering the Diaoyutai State Guest House in Beijing -- where he has stayed in the past and was expected to stay again this time.

It was unclear when the reclusive leader would meet Hu. Yonhap reported that what appeared to be the same motorcade was later seen coming out of Diaoyutai, heading towards the Great Hall of the People where talks often take place.

This prompted speculation Kim might be meeting Hu Wednesday evening, although sources had earlier told Yonhap summit talks between the two leaders would take place on Thursday.

Before his stop in Tianjin, the North Korean leader visited dock and industrial facilities in Dalian in the northeast -- suggesting he wants to learn how to boost his country's port cities as a way to increase trade.

"By visiting industrial sites, Kim is trying to learn about China's economic development," Kim Yong-Hyun, a North Korea expert at Dongguk University in Seoul, told AFP.

"The main and open goal of Kim's trip is to strengthen economic cooperation and secure more economic assistance from China," he added.

"In an attempt to overcome (economic) difficulties, Kim may tell China that North Korea is willing to resume six-party talks."

Cheng Xiaohe, a professor of international politics at Renmin University in Beijing, agreed, saying any aid given to Kim would be "aimed at getting him to return to negotiations".

The North has said it will not return to the six-party disarmament talks grouping the two Koreas, China, Japan, Russia and the United States until UN sanctions are lifted and the US agrees to talks on a formal peace treaty.

US and South Korean officials have said the sinking of a South Korean warship in March -- which was ripped apart by an external blast, killing 46 sailors -- has made an early resumption of negotiations less likely.

Seoul has hinted the Cheonan incident could be Pyongyang's fault. The North has denied all responsibility.

In Washington, State Department spokesman Philip Crowley said the next move on disarmament was up to North Korea.

"There are five countries on the same page with respect to the six-party process. There's one country that is not -- North Korea," Crowley said Tuesday, adding that China was in a prime position to make some headway with Kim.

"We would trust that if there are meetings with high-level Chinese officials that they will stress, as we do, that the only route forward for North Korea is through the six-party process."

Cheng said Kim would have to raise the Cheonan incident with Hu, as it was "slowly turning into a crisis that will impact China-North Korea economic exchanges and affect relations between China and South Korea".

Kim's trip to China -- his first in four years -- has not been officially confirmed by either Beijing or Pyongyang. An official at North Korea's embassy in Beijing told AFP Wednesday he had no information.

Both governments often refrain from comment until Kim, who reportedly suffered a stroke in mid-2008, is safely back home.

Kim, who is said to dislike air travel, has visited China four times since 2000, each time by train. It was not clear when this trip would end, but Hu is scheduled to begin a visit to Russia at the end of the week.

"His current trip to China appears to have a strong political and diplomatic motive, compared to his previous trips," said Kim, the expert at Dongguk University.

"North Korea now needs a breakthrough as its isolation from the international community has deepened, with its economic troubles worsening."