President Reagan's decisions on the future of the space program, including whether to build a new shuttle orbiter, probably will be postponed until after the National Aeronautics and Space Administration begins implementing the Rogers Commission report on the Challenger accident, administration sources said yesterday.

Although the White House had announced that Reagan might make a decision this week on the space program, the sources said it now appears that he will not act until next month at the earliest.

The commission, appointed by Reagan, was sharply critical of NASA management in the wake of the Jan. 28 accident that killed seven astronauts, and the White House has given the agency 30 days to devise a plan for implementing commission recommendations.

At the same time, an interagency group has been trying in recent months to produce options for Reagan on the program's future, including whether to build another shuttle orbiter, the need for unmanned rockets and how to deal with a growing space cargo backlog.

After months of deadlock, the interagency group has reportedly prepared a new options memo for the president. But officials said another high-level meeting on the subject may be held after Reagan returns from a six-day California vacation set to start today.

The officials said they had decided that it would be premature to make major decisions on the space program before addressing concerns raised by the commission.

"Can we honestly tell the American people we're going to repair the space program before we know how?" asked one administration official familiar with the space agency and White House deliberations.

Reagan said at his news conference June 11 that he thinks another shuttle orbiter should be built to replace Challenger, but many senior aides have questioned whether the cost can be justified.

White House chief of staff Donald T. Regan has been at the forefront of those asking whether the shuttle should be built or the money devoted to other high-technology space projects.

Space agency officials have sought to justify a new orbiter on grounds that it would provide "redundancy" to the existing fleet of three orbiters, but White House officials have been skeptical of this.

"We've decided the smart thing to do is take an appropriately skeptical look at everything involved in the space program" before proceeding, one knowledgable administration official said yesterday. "Let's look at everything and then come back to a decision."

NASA is supposed to have a plan by mid-July for implementing commission recommendations, officials said, but Reagan may wait longer before deciding on the future of the space program.

"The president does favor a fourth orbiter," presidential spokesman Larry Speakes said yesterday. "But he hasn't heard all the arguments. He may change his mind."

Meanwhile, NASA Administrator James C. Fletcher, Office of Management and Budget Director James C. Miller III and national security affairs adviser John M. Poindexter met yesterday to discuss budget aspects of the space program. Questions to be resolved include which agencies would bear the $1.9 billion cost of a new shuttle orbiter.

Staff researcher James Schwartz contributed to this report.