The July 2009 memo from the US embassy in Yangon said that Myanmar had exported about 20,000 tons of rice to North Korea through military-owned Myanmar Economic Holdings Ltd.

According to a well-placed business source, Myanmar "has been exporting rice and other agricultural commodities to North Korea for over five years in exchange for arms," added the cable, which referred to "conventional weapons".

US diplomatic memos released last year by WikiLeaks said Washington has also suspected for years that Myanmar ran a secret nuclear programme supported by Pyongyang.

A UN report published in November said North Korea was supplying banned nuclear and ballistic equipment to Myanmar, along with Iran and Syria.

Myanmar has dismissed reports of its nuclear intentions and brushed aside Western concerns about possible cooperation with North Korea.

A civilian administration has been nominally in charge of Myanmar since March, following a controversial election last year, but its ranks are dominated by former generals.

"The first batch of our flood relief aid is expected to be delivered next week," said South Korea's Ministry of Unification spokesman Chun Hae-Sung.

In early August Seoul offered flood aid worth five billion won ($4.7 million), including medicine, instant noodles, nutritious meals for children and other materials.

But it rejected the North's request for food staples, cement and equipment for restoration work. South Korea has been reluctant to ship rice or cement for fear it could be diverted to the military.

It was Seoul's first such offer since the North's deadly attack on a South Korean island last November sent relations into deep freeze.

Ties turned icy when Seoul accused Pyongyang of torpedoing a warship in March 2010 with the loss of 46 South Korean lives.

The North denied involvement in the sinking but shelled the border island last November, killing four people including two civilians.

The North, which even in normal times struggles to feed its people, has reported dozens of casualties, thousands homeless and large areas of farmland flooded following a storm and torrential rain this summer.

About 90 tonnes of emergency supplies sent by US-based Christian relief group Samaritan's Purse and funded by the US government arrived Saturday in the North.

It includes blankets, plastic sheeting for shelters, hygiene kits, water filtration systems and medical supplies.

For months Washington has been withholding a decision on sending separate food aid to the country until Pyongyang tackles US concerns over whether it will be distributed to the needy.