Washington, U.S. - The United States on Monday insisted the arrival in North Korea of a first shipment of US food aid had no link to Pyongyang's long-awaited declaration last week on its nuclear program.

'Look, there is zero linkage here,' said Mr Tom Casey, a State Department spokesman.

'Anyone asserting that there is a linkage either is extremely misinformed or malicious in intent.'

A US ship carrying tens of thousands of tonnes of food arrived in North Korea on Sunday, after the communist state authorized a big increase in overseas aid to its hungry people, the UN food agency said on Monday.

The World Food Program said in a statement it would in the future be able to feed more than five million people compared to the current 1.2 million.

It said a US-flagged ship arrived Sunday in the western port of Nampo carrying 37,000 tons of wheat, the first installment of 500,000 tonnes of food promised by Washington to the communist state earlier this year.

'We do not link food assistance, whether it is to North Korea or to Zimbabwe or any other country, to political considerations,' Mr Casey stressed.

'As far as I know, there is no one associated with the Six Party talks who had any say in this decision, any involvement in it, any participation in it,' the spokesman added.

The United States on May 16 announced an agreement with North Korea to resume food aid in June as Pyongyang faces persistent shortages.

Washington froze the assistance back in 2006, citing concerns about distribution. Now it sais NGOs are able to monitor distribution of US aid.

In Beijing, visiting US Secretary of State Condoleezza Rice said she was encouraged by recent developments in ending North Korea's nuclear weapons program, but warned much hard work remained.

'We're all encouraged,' she told reporters after holding talks with Chinese President Hu Jintao and Premier Wen Jiabao.

'(However) everybody emphasizes the hard work ahead,' she said.

Dr Rice's visit to China came after the North handed in a key declaration outlining its atomic activities last Thursday.

The declaration was part of a landmark six-nation deal reached last year, in which North Korea agreed to disable nuclear plants at its Yongbyon nuclear power plant in return for aid and diplomatic recognition.

The North on Friday also destroyed the cooling tower of its Yongbyon facility.

Dr Rice said the next round of six-party talks, held by host nation China, include the United States, Japan, South Korea, North Korea and Russia, and will take place 'pretty soon.' -- AFP