Despite Tuesday's statements by White House officials that the president was prepared to cut up to $30 billion from projected increases in military spending, a senior Pentagon official said today he was "absolutely certain that no decisions have been made" to actually make such cuts.

The official, who was traveling to Honolulu aboard a plane carrying Secretary of Defense Caspar W. Weinberger and who spoke with reporters under rules that he not be identified, said he didn't know why White House chief of staff James A. Baker III was talking publicly about such cuts nor would he speculate on Baker's motives.

The official said President Reagan had not told Weinberger there must be cuts in the Pentagon's planned five-year $1.6 trillion budget. The official told reporters he was not asserting there will or won't be cuts, but that Weinberger had assured himself positively that no decisions had been made yet and that "there is only one person who makes the decisions," meaning the president.

Despite what the official described as "a lot of discussion" at the western White House headquarters in recent days, "I guess we are in a situation where we'll have to wait until all the facts are in."

[President Reagan said in Chicago tonight that his willingness to trim projected defense spending by as much as $30 billion in fiscal 1983 and 1984 is not a retreat from his goal of a rapid buildup of U.S. military forces, and he issued a tough warning to the Soviet Union about future arms negotiations.]

[Speaking at a Republican fundraiser, Reagan said that unless the Soviets are willing to accept a "legitimate, . . . verifiable arms reduction, they will be in an arms race which they can't win."]

[He said later that he was not threatening the Soviets and was not prepared to insist that on-site inspection verify any arms treaty.]

[Reagan said the defense budget would not be spared future cuts but added: "That does not mean we are retreating from the program we adopted of an annual 7 percent increase in defense spending to restore our defensive capability and close that window of vulnerability that has been opened in recent years with the superiority of the Soviet forces."]

[He said the United States would urge the Soviets to discuss arms reduction but warned that his administration would insist on verifiable reductions and back that with a powerful military force.]

The comments of the senior Pentagon official, who said specifically he was not bitter at the public remarks by Baker, underlined the deep divisions within the administration over the defense budget, which Reagan has termed one of his "overriding priorities." Weinberger is expected to make a spirited defense of his five-year plan, especially the programs he considers essential for "rearming America as strongly as possible."

The senior Pentagon official also said that Weinberger had not been in communication with Baker in the aftermath of Baker's comments.

Baker's remarks were repeated, however, by deputy White House press secretary Larry Speakes on Tuesday, providing additional indications that the White House was indeed leaning toward substantial reductions in the rate at which the Pentagon's budget will increase.

Today's comments raise the possibility that the Pentagon, including Weinberger, had not been made aware of the president's inclinations or that White House officials spoke prematurely.

The senior Pentagon official said he expected the president would decide on the defense budget question within a week or two and that Weinberger expected to have an opportunity to present his case to the president before then.

The senior official also said that while the Pentagon was not reconciled to a smaller budget rise, the Defense Department and the armed forces were looking at a number of different funding levels and were reassessing their priorities in the event Reagan does decide to reduce the current spending plan.

The official said the Pentagon at this point was looking more at what individual programs might be altered than at specific annual budgets, and he declined to say whether the current fiscal 1982 budget already on Capitol Hill would come in for some reductions.

On other matters, the senior official said the final decision on what to do about the Air Force's new MX missile had not been made but probably would be within a couple of weeks after Congress returns.

Weinberger's plane stopped here en route to an American Legion convention in Honolulu, which the secretary will address tomorrow.