NAYPYITAW, Myanmar — U.N. Secretary-General Ban Ki-moon, on a mission to open Myanmar to international disaster assistance, said the ruling junta agreed today to allow "all aid workers" into the country to help survivors.

Ban's comments came after a crucial two-hour meeting today with the junta leader, Senior Gen. Than Shwe, the country's most powerful figure. Myanmar's junta has until now refused to allow an influx of foreign aid and experts to reach survivors of Cyclone Nargis, which struck three weeks ago and killed at least 78,000 people and left 56,000 missing.

The United Nations chief did not say whether Than Shwe had acceded to the most urgent request by international aid agencies — to allow their foreign experts into the hardest-hit region, the Irrawaddy delta.

However, when asked if he thought the agreement was a breakthrough, Ban told reporters: "I think so." One foreign aid official called it a "significant step forward."

A senior U.N. official present at the meeting said Than Shwe also gave the green light for foreigners to work in the hardest-hit region, the Irrawaddy delta, which has been virtually off-limits to them.

Ban "saw no reason why that should not happen, as long as they are genuine humanitarian workers and it was clear as to what they were going to be doing," said the official, who requested anonymity for reasons of protocol.

The official said government authorities had earlier not been able to give this assurance of access because they needed a "green light from the top."

Myanmar's military government has until now refused to allow an unimpeded influx of foreign aid and experts to reach survivors of the May 2-3 Cyclone Nargis.