United Nation, May 10 : The United Nations has urged the authorities of Myanmar to be flexible in opening their boundaries so that aid workers could reach to several victims of cyclone Nargis.

Secretary-General Ban ki-Moon in a statement expressed disappointment at the limited access to Myanmar where thousands of people are in desperate need of relief supplies.

Launching the 187-million doolar appeal, Ban warned that the lives of those who survived a deadly cyclone could be at risk if the military leaders refuse international aid.

"If early action is not taken and relief measures put in place, the medium-term effect of this tragedy could be truly terrible," he said.

"It emerged that Ban had not yet been able to contact General Than Shwe, the head of the Myanmar junta, due to severe damage to the country's telecommunications infrastructure," a UN source said.

Meanwhile German Chancellor Angela Merkel demanded the UN Security Council unite to push Myanmar to open up to international aid -- despite objections from China.

"I strongly urge the government to assume the responsibility it has to its people and to allow international aid into all the regions hit by the disaster," she said.

Two World Food Program relief flights are due to arrive in Myanmar today, whilst a US military cargo plane carrying supplies is expected to arrive there Monday.

International aid groups said help was slowly arriving for most of those in the stricken southwest Irrawaddy delta who saw their villages ripped apart or washed away.

The UN said four disaster experts received permission to travel to Myanmar, but there was no immediate word for others awaiting a green light from the military.

Food prices in Myanmar, already one of the world's most impoverished nations, have soared. A bag of rice now costs 40,000 kyats (35 dollars) in the commercial hub Yangon, up from 25,000 last week.