US space agency Nasa said Friday that it was leaving the door open to reviving the cancelled plan to conduct a climate study from U-tapao naval airbase.

But Thai authorities insisted the plan would then have to undergo a new round of consideration.

No decision has been made "on whether Nasa will be able to fly the mission next year or sometime in the future", said Steve Cole, a Nasa spokesman in Washington.

Nasa scrapped the study after the Thai government delayed action on a request to use U-tapao air base as its operations centre for atmospheric observation during the peak Asian monsoon season.

The opposition Democrat Party had charged that US use of U-tapao, a launchpad for US B-52 bombing missions during the Vietnam War, would infringe on Thai sovereignty, among other things.

Mr Cole said there were a range of options other than U-tapao, both inside and outside Thailand, that could perhaps serve as headquarters for a future study.

''But I don't want to give the impression that Nasa is actively considering specific locations,'' he said. ''We are not yet at that stage.''

Nasa had sought to operate the mission from U-tapao's airfield because of its central geographic location, access to infrastructure and cost considerations, Mr Cole said.

Without basing approval in hand on June 26, the timeframe was too short to get the mission in the field to study the conditions in August and September, ''when unique atmospheric processes occur that were the focus of the campaign'', he said.

Navy commander Surasak Rounroengrom said if Nasa wants to revive the project at U-tapao airport, its request must go through a fresh consideration process.

He said the navy will take into account security aspects and there will be a committee to handle the request.

''It'll undergo a similar process. We'll examine how the project will benefit the country first and then review the request to use U-tapao airport,'' Adm Surasak said.

He insisted that no Nasa equipment was being housed in the naval airbase.

He said the issue had been clarified by Royal Thai Fleet commander Kanat Thongpoon and navy chief-of-staff Darongsak Haocharoen.

When asked if the navy feels uncomfortable about the politicising of the request to use U-tapao, Adm Surasak said there were no hard feelings.

He said the navy did what it was supposed to do, especially when it came to protecting national security.

Prime Minister Yingluck Shinawatra said the government would proceed with its plan to submit the Nasa project for parliamentary debate despite the cancellation of the project.

She said scrutiny resulting from the debate could be useful if Nasa decides to revive the project next year.

''It is possible that the findings [from the debate] will be of use if the cabinet is asked to reconsider the issue,'' Ms Yingluck said.

The debate is set to take place in August when parliament reconvenes.

Chief government whip Udomdej Rattanapian agreed with Ms Yingluck, and said government whips were expected to consider pushing for a House session on the issue next week.

Mr Udomdej also voiced concern about a possible movement to exploit the Nasa issue to topple the government.

Deputy Prime Minister Yutthasak Sasiprapa, however, said there was no need for a parliamentary debate on the issue unless Nasa resubmits the request.

''There is no need to consider it in advance. If they don't make a request, it is a waste [of time],'' he said.

Former foreign minister Noppadon Pattama said the government made the right call by putting off the decision because Section 190 of the constitution _ which states any agreement or treaty affecting the national interest or sovereignty must be approved by parliament _ could be interpreted very broadly.

''The section is a landmine and the Constitution Court's interpretation is unpredictable,'' he said.

He called for amendment of the section, which he said was hampering government activities.