Despite President Reagan's statement that the United States should build another space shuttle to replace Challenger, there is a growing consensus among senior officials that a fourth orbiter cannot be justified, administration officials said yesterday.

At his nationally televised news conference Wednesday night, Reagan, questioned about whether he has decided to support building a replacement orbiter, mentioned some of the problems confronting the space program and then said, "Yes, I think we should go forward with another shuttle."

But officials said yesterday that the president has not decided to do so and that his senior advisers are increasingly skeptical of the need for the craft. "In his heart, he wants it," one senior official said. "In his head, he knows the problems."

According to this official, space agency Administrator James C. Fletcher has balked at absorbing the entire $2.8 billion cost of a fourth orbiter. The official said Fletcher indicated to White House officials that, with limited resources, he would give higher priority to the manned space station project. The National Aeronautics and Space Administration had previously pushed for a orbiter.

National security affairs adviser John M. Poindexter, who is overseeing the preparation of an options paper for Reagan, is described by officials as "rethinking" the need for a fourth orbiter. White House chief of staff Donald T. Regan has repeatedly questioned the need for it.

"Everybody is coming in that direction," said a White House official who cautioned, however, that the decision could be affected by members of Congress who support the shuttle.

Officials said that Reagan's news conference statement was not intended to be a commitment to build another orbiter. Only a few weeks ago, Reagan had been expected to approve the construction of a fourth orbiter soon, but the officials said that is now far less certain. "It's really up in the air," one said.

Meanwhile yesterday, members of a House committee, contending that "substantial" questions about the Challenger accident remain unanswered, demanded to know why top NASA officials failed to respond to clear-cut warnings last August about problems with the solid rocket booster seals, blamed for the Jan. 28 disaster that killed seven crew members.

Shuttle director Richard H. Truly acknowledged, after repeated questioning from Rep. James H. Scheuer (D-N.Y.), that blame for the accident should not be limited to officials at the Marshall Space Flight Center in Huntsville, Ala., and that NASA headquarters had sufficient information by August to require that the booster joints be fixed.

"This went right up to NASA's nerve center in Washington," Scheuer told Truly and Fletcher during a hearing of the House Science and Technology Committee. "It's not a question of you should have been alerted. You were alerted . . . ."

Much of the testimony centered on an Aug. 19 briefing on the booster seals that was given to Michael Weeks, the shuttle's chief technical administrator. The Rogers commission, which investigated the Challenger accident, concluded that the briefing was "sufficiently detailed to require corrective action prior to the next flight," but did not name those at the meeting.

Testifying for the first time in public, Weeks said he did order some corrective steps but was told that it would take two years to repair the booster joints completely. He said that "in hindsight" he should have taken stronger action.

Yesterday's testimony came as committee members indicated that they were not satisifed that the Rogers commission had answered all their questions about the accident.

Rep. Robert A. Roe (D-N.J.), who is chairing the hearings, said that "substantial data" on the accident were not included in the commission's report and that the House panel intends to pursue the matter.