President Reagan's determination to have the first MX intercontinental ballistic missiles operational by December, 1986, is forcing the Air Force to take shortcuts in building the missile and its bases.

"With all of the delays, reviews and reprogrammings in the program we have never had that initial operational capability date taken off our back," Maj. Gen. Clifton D. Wright told a House subcommittee earlier this year. Wright is in charge of building facilities for the MX deployment.

Another problem area is in meeting testing deadlines. Despite Friday's first successful flight of an MX, the overall test program already is six months behind its original schedule.

The 1986 date, when the first 10 MX missiles were to be operational, was set five years ago by President Carter. His plan was to build 200 MXs and hide them among 4,600 shelters in Nevada and Utah.

In 1981, President Reagan scrapped the Carter basing plan and halved the number of MXs to be built, but retained the 1986 operational date for the first missiles.

Last year, when Congress balked at funding initial MX production, the administration argued the money was needed to have the first missiles ready in 1986. When Reagan organized his commission on strategic forces in January, his directives were that he wanted MX built and deployed in such a way that it would become operational by 1986.

Last week, the question of the MX initial operating date came up on the Senate floor when supporters of the missile tried to push forward an amendment to allow design work to begin on a key building plan for Warren Air Force Base in Wyoming.

Because of an amendment passed last year, design for the building in which missiles will be assembled and warheads put in place cannot begin until an environmental impact statement has been completed.

MX supporters tried to get that language changed because, they said, a delay of just three months in designing the building could delay the December, 1986, operational date.

Sen. Carl Levin (D-Mich.) defeated the amendment, arguing, "We should not have an operational date on this MX which is artificial . . . . We are not going to cut corners on the construction of the MX to make an artificial" deadline.

The Air Force, arguing that it would be difficult to meet construction deadlines without immediately starting design, said in a "point paper" offered to Congress that building schedules "have already been compressed to the maximum" and that construction had to begin by August, 1984, to meet the 1986 date.

Concerns about meeting the deployment deadline come as the MX, in its first test, soared to a 4,700-mile maiden flight over the Pacific despite attempts by peace activists to stop the test.

The missile roared aloft over the California coast Friday and 30 minutes later dropped six dummy warheads near Kwajalein Atoll. Air Force officials said the missile performed "exactly" as expected.

Meanwhile, Air Force officials revoked Vandenberg base credentials for reporters of two California news organizations, KFWB radio and the Santa Maria Times, for breaking an Air Force embargo against using the launch story. Publisher Walt Rosebrock of the Times said the launch was common knowledge.