* Two more U.S. flights arranged for Tuesday

* Aid deliveries to survivors minimal so far, agencies say

* Bush calls junta either "isolated or callous"

* Myanmar to grant U.N. 34 visas

By Aung Hla Tun

YANGON, May 13 (Reuters) - Two more American aid flights were due to leave for cyclone-hit Myanmar on Tuesday where the reclusive military government is keeping most foreign aid workers away from the devastated Irrawaddy delta.

Local staff for international relief agencies are stretched to breaking point and facing tighter restrictions on their ability to deliver a trickle of foreign aid to 1.5 million people facing hunger and disease.

Medicins Sans Frontieres (MSF) said its first cargo plane loaded with medical and logistical supplies landed in the former capital Yangon on Monday. But it was facing "increasing constraints" imposed on its workers in the delta.

"In Bogalay for instance, the MSF team is unable to provide as much assistance as they could to respond to the enormous needs in terms of food and medical care," the aid group said of one devastated township where at least 10,000 people were killed.

The military junta has welcomed "aid from any nation" but has made it very clear it does not want an influx of foreign experts or equipment to distribute it in five declared disaster zones after Cyclone Nargis struck 11 days ago.

U.S. President George W. Bush, speaking after the first u.S. military aid flight to Myanmar on Monday, condemned the junta for failing to act more quickly to accept international help, saying "either they are isolated or callous."

Bush, who before the cyclone had imposed fresh sanctions on the country ruled by the military for 46 years, said the junta was apparently more interested in power than in its people.

"It's been days and no telling how many people have lost their lives as a result of the slow response," Bush said in a radio interview with CBS News. "An American plane finally went in but the response isn't good enough."

The C-130 military transport plane flew in from an air base in neighbouring Thailand carrying water, mosquito nets and blankets, but U.S. officials involved in the relief effort were not allowed beyond Yangon airport.

A stream of other aid flights had already landed in Yangon, but only a fraction of the help is getting to where it is needed.

The World Food Programme said it was able to deliver less than 20 percent of the 375 tonnes of food a day it wanted to move into the flooded delta.

WAITING FOR VISAS

At the United Nations in New York, Ban delivered his most critical comments so far of the Myanmar authorities' response and said: "We are at a critical point."

"Today is the 11th day since ... Nargis hit Myanmar," he told reporters. "I want to register my deep concern -- and immense frustration -- at the unacceptably slow response to this grave humanitarian crisis."

The United Nations said its top representative in Myanmar had flown to Naypyidaw, the generals' new capital, on Monday to hand over a list of 60 critical U.N. and relief agency staff.

U.N. humanitarian affairs chief John Holmes told reporters in New York the United Nations had disbursed $20.3 million from its emergency relief fund to cover costs related to urgent needs, such as food, shelter, sanitation and health.

He said there were still problems with visas though the situation had improved somewhat. "It was confirmed that 34 visas for United Nations relief staff from the different agencies will now be granted or are being granted," he said.

In its latest assessment of the scale of the disaster, the U.N. humanitarian agency said between 1.2 million and 1.9 million people were struggling to survive and the number of dead could range from 60,000 to 102,000.

Myanmar state television raised its official toll to 31,938 dead and 29,770 missing on Monday. Most of the casualties were killed by the 12-foot (3.5 metre) wall of water that hit the delta, with the cyclone's 190 kph (120 mph) winds.

People throughout the delta were crammed into monasteries, schools and other buildings. Displaced people flooded into towns that were barely able to cope with the influx.

Lacking food, water and sanitation, they faced diseases such as cholera. Heavy rain was forecast for the delta this week, which could further hinder the relief effort.

People from Yangon were loading food and water into their vehicles and taking it to villages outside the city in the absence of any organised aid effort.

The cyclone raged through an area that is home to nearly half of the country's 53 million people and about 5,000 sq km (1,930 sq miles) of land remained under water. The cyclone ravaged some of the country's main rice-growing areas.

France was sending a warship carrying 1,500 tonnes of rice which was expected near Myanmar later this week. Paris says it wants to distribute the food directly itself, but will not do so without authorisation.

The United States will also have three ships near Myanmar this week, and Britain was sending a navy ship to the region to help humanitarian operations. (Additional reporting by Louis Charbonneau and Patrick Worsnip at the United Nations; and Susan Cornwell and Paul Eckert in Washington; Writing by Darren Schuettler; Editing by Bill Tarrant)

AlertNet news is provided by