BANGKOK: The United States says it will not be able to carry out a major climate study this year because Thailand has delayed a decision on whether to grant the US space agency permission to use a key naval air base.

NASA's request to use Thailand's U-Tapao air base as the project's operations center has faced opposition from critics who say it could be a cover for military purposes. The base is located in Chonburi province, 190 kilometers (118 miles) southeast of Bangkok.

''It is too early to say at this time whether resources will be available to revisit the project next year,'' US Embassy spokesman Walter Braunohler told The Associated Press on Thursday.

The project, called the ''Southeast Asia Composition, Cloud, Climate Coupling Regional Study,'' was to use satellites, aircraft and ground missions to study how air circulation during the monsoon affects the climate and air quality in South and Southeast Asia.

Thai scientists involved in the project were skeptical that NASA would pursue its mission in Thailand next year.

''It's a great loss for Thailand to lose a vital opportunity to learn what we should know about regional climate, including floods, drought and other catastrophes,'' said Serm Janjai, a physics professor at Thailand's Silpakorn University involved in the project.

''But what is more important is it has destroyed confidence in Thailand among the international science community. Someone has to take responsibility for this failure.''

NASA said it canceled the mission Tuesday ''due to the absence of necessary approvals by regional authorities in the time frame necessary to support the mission's planned deployment and scientific observation window,'' according to the project's website.

Thailand's Cabinet had agreed Tuesday to have lawmakers debate the issue before deciding on whether to grant permission for the project. However, Parliament does not reconvene until August 1 – a month after NASA's deadline for a decision.

U-Tapao was a major base for US bombing missions during the Vietnam War, and some critics have charged that the NASA project is a threat to Thai sovereignty and that it might also anger China. The US military has continued to use the base for refueling and as a staging area for humanitarian relief operations, including those conducted after the 2004 Indian Ocean tsunami and Myanmar's 2008 Cyclone Nargis.

The NASA project would have studied carbon emissions in the region in August and September, when regional monsoons could carry wildfire smoke from Indonesia and Malaysia north to countries such as Thailand.

Critics of the project include nationalists and the opposition Democrat Party. There have been allegations, unsupported by evidence, that the project would be a cover for US military and intelligence activities. NASA and scientists supporting the project have pointed out in rebuttal that its details were openly available.