European space scientists say they're rethinking potential space missions after learning NASA won't be contributing significant funding to any of their efforts.

Three proposed missions -- the International X-Ray Observatory, a Europa-Jupiter probe known as EJSM-Laplace, and a space-based gravity wave detector called LISA -- have been developed with NASA as a potential partner, but the cash-strapped U.S. space agency has told the European Space agency it has higher priorities for its limited space science budget, AAAS ScienceMag.org reported Friday.

NASA's decision "means in principle that none of the three missions is feasible for ESA," Xavier Barcons of the Cantabria Institute of Physics in Spain said.

ESA has said it will try and proceed on its own, delaying its commitments to any of the missions until 2012.

The agency has asked each mission group if a significant fraction of the science goals in their respective mission can be preserved within Europe's planned budget.

"We've given them a year to come up with the answer," Fabio Favata, head of ESA's science planning office, said.

Scientists on the three missions are reviewing what can be cut from their projects.

"It is disappointing ... all three missions will have difficulty now, and all three will have delays and redesigns," physicist Karsten Danzmann of the University of Hannover in Germany, who is the European chair of the LISA International science team, said.