The United Nations and the Association of Southeast Asian Nations (ASEAN), of which Myanmar is a member, are to convene a donors' pledging conference in Yangon on Sunday.
The government wants more than $11 billion in aid, but international donors need access to verify the needs, ASEAN Secretary-General Surin Pitsuwan told Reuters in an interview.
"Accessibility is important to guarantee confidence and verify the damage and needs, otherwise confidence during pledging will be affected," Surin said on a visit to Yangon.
Ban was due to meet Myanmar ministers involved in the relief effort before flying to the delta later on Thursday.
The U.N. chief will meet junta leader Than Shwe in Naypyidaw, a new capital 250 miles (390 km) north of Yangon, on Friday.
Than Shwe, who took two weeks after the disaster to meet victims and see the destruction for himself, had declined to take Ban's phone calls earlier in the relief effort.
Bangkok-based political analyst Thitinan Pongsudhirak said expectations from Ban's trip will be fairly low. "He is arriving on the scene very late in the equation where many lives have been been lost unnecessarily in the interim."
However, Yangon diplomats say the general's appearances in public this week, visiting several delta towns, could be a sign the top brass finally realize the enormity of the destruction and recovery from one of the worst cyclones to hit Asia.
The first of nine helicopters granted permission to airlift supplies into the delta was due to arrive in Yangon on Thursday, the World Food Programme said.
The United Nations says up to 2.4 million people are struggling to survive in Yangon and the Irrawaddy Delta, where refugees have been begging for food from relief workers.
Permission for the WFP helicopters is one sign the junta is starting to make small but -- in the case of one of the world's most closed countries -- unprecedented concessions to foreign governments and relief agencies wanting to help.
But a commentary in the junta's main voice, the New Light of Myanmar, said on Wednesday that "strings attached to the relief supplies carried by warships and military helicopters are not acceptable to the Myanmar people. We can manage by ourselves."
European Union lawmakers kept up pressure on Myanmar's military, which has ruled the former Burma for 46 years.
The European Parliament, which has no legal power over the bloc's foreign policies but can help shape opinion in the bloc, will vote on a resolution on Thursday urging the U.N. Security Council to consider whether forced aid shipments were possible.
"The Burmese authorities are responsible for a crime against humanity," Polish EU lawmaker Urszula Gacek said.
The generals' distrust of outsiders is even greater after worldwide outrage at last year's crackdown on democracy protests. U.N. sources say they have consistently declined offers of Thai, Malaysian and Singaporean military helicopters.
The government's official toll is 77,738 people killed and 55,917 missing, and it also estimates the damage to one of Asia's least-developed economies at $10 billion.