The senator was due to fly to the country Thursday but said it would be "unwise and potentially counter-productive" until there is further clarification on accusations. The findings "contain new allegations regarding the possibility that the Burmese government has been working in conjunction with North Korea in order to develop a nuclear programme", Webb said.
The Doho based news and current affairs channel Al Jazeera said evidence came from top-secret material smuggled out of the country over a period of several years.
The investigation lasted for years and included hundreds of files and other evidence from a Myanmar defector, army major Sai Thein Win, who said he was deputy commander of a military factory heading up Myanmar's nuclear battalion.
"They really want to build a bomb. That is their main objective," he is quoted as saying in the film.
Myanmar, which has been military-ruled since 1962, has previously been accused of violating a UN Security Council ban on North Korean arms exports, which was imposed last June.
President Barack Obama's administration last year launched a dialogue with Myanmar's military rulers, after concluding that Western attempts to isolate the regime had met with little success.
But Washington has sharply criticised preparations for this year's elections, which are expected to be held in October and the first in 20 years, as well as raising nuclear worries.