President Carter will announce his decision on the future of the B-1 bomber today amid increasing speculation that he will reserve a campaign promise and approve at least limited production of the controversial and costly aircraft.

The decision will be announced at a nationally televised news conference at 10:30 this morning, to be broadcast live on channels 4, 7 and 9. The speculation and hints of what the decision will be came from such diverse sources as members of Congress, Defense Secretary Harold Brown, Carter confidant Charles Kirbo and members of the White House staff.

Emerging with a group of senators from a breakfast meeting with the President, Sen. Jennings Randolph (D-W.Va.) said he believes Carter will approve production of "a substantial number" of the bombers, "much more than has been discussed."

Dicussions up to this point have centered on producing between 100 and 170 of the bombers, instead of the 244 sought by the Air Force.

In Atlanta, meanwhile, Kirbo, the President's closest friend and personal adviser, told Washington Post staff writer David S. Broder that Carter's campaign opposition to production of the plane would not be the controlling factor in the decision.

" . . . Most people realize that in the defense area you make statements based on your information at the time," he said. "But when the national interest is concerned, you do what the country's needs require. I'd hate to think we'd have a President who didn't do what was best for the country as he sees it now, not sometime in the past."

Kirbo, who said he thought he knew what the decision would be, defense policy is one area where it is possible to make "adjustments" from campaign promises.

Suggesting two possible justifications for approval of the plane, Kirbo said Carter could argue that he has "new information or the benefit of the thinking of experts" that made him modify his position, or he could say it was "because of the position the Russians are taking or something they have done."

The President met for 30 minutes with Brown yesterday for a final review of the decision. Asked afterwards whether he and Carter are in agreement about the decision, Brown smiled broadly and said, "Sure."

Brown is known to be an advocate of the B-1.

The hints from White House aides, none of them were privy to the decision, came in the form of gloomy predictions in recent days by those who personally oppose production of the bomber. "I have a feeling something bad is coming," one of them said.

The 244-plane fleet of B-1s being sought by the Air Force would cost an estimated $24.8 billion. Each of the aircraft is estimated to cost more than $100 million.

The decision is a politically difficult one for the President because of his campaign rhetoric and because a decision for even limited production is bound to anger the liberal wing of the Democratic Party.

Last July, Carter told the Democratic National Convention Platform Committee, "The B-1 bomber is an example of a proposed system which should not be funded and would be wasteful of taxpayers' dollars."

In another development yesterday the President announced the beginning of four new studies of government functions as part of the government reorganization effort. The studies, to take five to nine months, will deal with law enforcement, local and community economic development, human services and administrative services.