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The United Nations said Tuesday it would soon decide whether to release emergency humanitarian funds for North Korea as a U.S. government team arrived in the secretive Asian nation to assess its request for food aid.

The U.N. World Food Program launched a $200 million dollar international appeal late last month after it concluded that 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.

But donor response appears to have been weak because of distrust of North Korea's communist regime and concern that assistance might be diverted to its powerful military. South Korea is skeptical that the situation is so dire — an opinion shared by critics of the North in Washington.

Four U.S. senators have urged the Obama administration to show extreme caution in assessing the North's request for food, saying giving aid would bolster Kim Jong Il's regime.

Kim is on a rare trip abroad, reportedly studying economic reforms in China, North Korea's sole major international ally.

U.N. humanitarian chief Valerie Amos stressed at a news conference at U.N. headquarters that humanitarian aid "is all about need — it is not about the political agenda in any one country."

Based on the World Food Program's assessment, Amos said she will make a decision "very soon" on releasing money from the U.N.'s Central Emergency Response Fund for North Korea. The fund, which was established to provide immediate aid for humanitarian emergencies, has probably been the biggest supplier of humanitarian aid to North Korea in the last few years, she said.

Amos said she hasn't determined how much aid the U.N. might provide to the North, but she said "it will only be a fraction of what is required."

"We've had a lot of difficulty raising money for North Korea because so many member states are concerned about the political situation there," Amos said. "We will continue to bring to the attention of member states the humanitarian situation as we see it, the needs in the country as we see it, and try to raise money to ensure that the essential food, but also other basic supplies that are required, are able to go in."

The American delegation — led by Robert King, U.S. special envoy for North Korean human rights issues — arrived in Pyongyang on Tuesday. It 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.

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

This is the first visit by an American human rights envoy to the North, though King himself traveled to the country as a congressional aide. Pyongyang detested King's predecessor, the first to hold the post. Jay Lefkowitz was a harsh critic of the country's rights record and even took aim at his bosses in the George W. Bush administration for pursuing nuclear disarmament talks.

King is more measured in his comments.

What some believe is a dire need for food in the North may also have played a part in the decision to allow King in.

North Korea asked for assistance in January following summer floods that hit staple crops and in the midst of a bitter winter. While humanitarian organizations say aid is urgently needed, there is widespread international distrust of the North Korean government, which has pursued illicit nuclear weapons and missile programs despite its chronic food shortages.

North Korea suffered a famine in the 1990s due to mismanagement of its centrally-controlled economy and natural disasters.

In a letter to U.S. Secretary of State Hillary Rodham Clinton, obtained by The Associated Press, the four senators, led by independent Joe Lieberman, said: "We believe we must be extremely cautious not to allow the North Korean government to manipulate the issue of food aid, as it has done in the past, as a political weapon."

The North Korean leader's trip to China began Friday night. It is Kim's third trip to China in just over a year.

China has provided diplomatic cover for the isolated hardline regime and is keen to see North Korea reform its moribund planned economy to head-off instability.

South Korea's Yonhap News agency said Kim arrived in the ancient Chinese capital of Nanjing from nearby Yangzhou, where he reportedly visited an industrial park and a shopping center on Monday.

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

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. Previous reform attempts have been abandoned by North Korea 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.

North Korea's exchanges with China have grown even more important since South Korea's conservative government halted unconditional food and fertilizer shipments in early 2008 and suspended almost all trade with the North. The U.N. and others have also enacted sanctions to punish the country for violating nuclear agreements.

The last U.S. food shipments were stopped in 2009 after nuclear monitors were expelled.

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Bodeen reported from Bejing. Associated Press writers Foster Klug in Seoul, South Korea, and Matthew Pennington in Washington contributed to this report.