CAPE CANAVERAL, Fla. The House Appropriations Committee proposed Wednesday to kill the James Webb Space Telescope, the crown jewel of NASA's astronomy plans for the next two decades.

The telescope, named after a former administrator of the National Aeronautics and Space Administration, is the successor to the Hubble Space Telescope and was designed to study the first stars and galaxies that emerged in the first hundred million years or so after the Big Bang.

It was supposed to be launched in 2014, but NASA said last year that the project would require at least an additional $1.6 billion and several more years to finish, because of mismanagement.

Just last week, NASA announced that it had finished polishing all the segments of the telescope's mirror, which is 6.5 meters in diameter, but the agency has still not announced a new plan for testing and launching the telescope.

The announcement of the telescope's potential demise came as part of a draft budget for NASA and other agencies, including the Commerce and Justice Departments. In all, the committee proposed lopping $1.6 billion off NASA's current budget, which is $18.4 billion for 2011. The Obama administration had originally requested $18.7 billion for NASA.

Astronomers reacted with dismay, fearing that the death of the Webb telescope could have the same dire impact on U.S. astronomy that killing the Superconducting Supercollider, a giant particle accelerator in Texas, did in 1993 for U.S. physics, sending leadership abroad.

Canceling the Webb telescope would "have a profound impact on astrophysics far into the future, threatening U.S. leadership in space science," said Matt Mountain, director of the Space Telescope Science Institute, in Baltimore, which would run the new telescope. "This is particularly disappointing at a time when the nation is struggling to inspire students to take up science and engineering."

Tod Lauer, an astronomer at the National Optical Astronomy Observatory in Tucson, echoed his view.

"This would be an unmitigated disaster for cosmology," he said. "After two decades of pushing the Hubble to its limits, which has revolutionized astronomy, the next step would be to pack up and give up. The Hubble is just good enough to see what we're missing at the start of time."

The Webb telescope, he said, "would bring it home in full living color."

The Appropriation Committee's proposal was the opening act in what is likely to be a long political drama, in which the Senate will eventually have a say. The measure is expected to be approved today by the subcommittee in charge of NASA and the other agencies, according to Jennifer Hing, a spokeswoman for the committee.

Next Wednesday, the full Appropriations Committee will meet again to consider the final bill.