Updated

BEIJING -- A U.S. government team was in North Korea to assess food shortages Tuesday, while the country's reclusive leader Kim Jong Il reportedly traveled to an eastern China city on a visit aimed at studying Beijing's economic reforms.

The delegation -- led by Robert King, U.S. special envoy for North Korean human rights issues -- will use its five-day visit to verify food supply surveys conducted by the United Nations and U.S.-based charities and see if there are ways to monitor aid distribution.

North Korea asked for food assistance in January after summer floods and during a bitter winter that hit staple crops. While humanitarian organizations say aid is urgently needed, the U.S., like other international donors, distrusts the secretive North Korean government, which has pursued illicit nuclear weapons and missile programs despite its dire food shortages.

A U.N. World Food Program assessment released two months ago found more than 6 million of North Korea's 23 million people were in urgent need of aid. It said the North's public distribution system would run out of food between May and July.

South Korea is skeptical that North Korea's situation is so dire and suspects the government is stockpiling food secretly ahead of the 2012 centennial of the birth of the communist nation's founder, Kim Il Sung

While King's trip was announced well in advance, virtually nothing is known about the agenda for Kim's visit to his country's most important ally, which began Friday night. Beijing and Pyongyang delay publicity about Kim's visits until after he has crossed back into North Korea.

South Korea's Yonhap News agency said Kim arrived in the ancient capital of Nanjing from nearby Yangzhou, where he reportedly visited an industrial park and a shopping center on Monday. It said his train departed at about 2 p.m. (0600 GMT) headed north in the general direction of Beijing.

Kim is also believed to have met with Vice President Xi Jinping, who is expected to be China's next leader, and former President Jiang Zemin, and is expected to also travel to Shanghai.

Unusually for China, Premier Wen Jiabao has confirmed that Kim is in the country, saying China invited him to study and hopefully adopt Beijing's market-oriented reforms that have transformed the economy into the world's second largest.

Kim's third trip to China in just over a year seems to indicate he is interested in better understanding China's success amid chronic shortages of food, fuel and other basic necessities in the North. China has provided diplomatic cover for the isolated hardline communist regime and is keen to see North Korea reform its moribund planned economy to head-off instability resulting from an explosive mix of poverty and repression.

However, previous reform attempts have been abandoned and it's far from clear how far the ailing 69-year-old Kim -- or his anointed successor, son Kim Jong Un -- would be willing to go.

The question of whether Kim Jong Un was traveling with his father remained unresolved Tuesday, with China's official Global Times newspaper saying that the younger Kim was not in the delegation to Yangzhou.

North Korea's exchanges with China have grown even more important since ties with South Korea soured after a new government took office in Seoul in 2008 and the U.N. and others enacted sanctions to punish the country for violating nuclear agreements.

South Korea's conservative government halted unconditional food and fertilizer shipments in early 2008 and has suspended almost all trade, costing the North tens of millions of dollars annually in lost income. The last U.S. food shipments were stopped in 2009 after nuclear monitors were expelled.

The U.S. State Department said while in North Korea, King would also raise human rights concerns and the detention of U.S. citizen Eddie Jun, who was arrested in November.