Mayor Marion Barry yesterday signed the $1.89 billion fiscal 1983 operating budget approved by the D.C. City Council, despite having threatened two weeks ago to veto the measure because it was not legally balanced.

In defending his reversal, Barry insisted that the City Council had significantly amended its budget report to assure there would be sufficient tax revenues to cover planned spending. "This budget is balanced in that it satisfies the minimum threshold requirements of the City Charter," Barry said at a news conference.

Barry said he also concluded there was little to be gained from provoking a crisis and prolonging the city's budgetary process, particularly when there appeared to be enough votes on the council to override a veto.

Council Chairman Arrington Dixon said he was pleased by what he said was the mayor's new-found spirit of cooperation. But he added that Barry may have inadvertently provided additional ammunition to critics who say his administration lacks credibility in handling city finances.

"I think it's clear some people could raise the concern about the credibility of this action as compared to his previous statements," said Dixon, who played a major role in shaping the final version of the budget.

On Feb. 17, a seemingly combative Barry stated unequivocally that he would veto the budget unless the council immediately approved $11.6 million in additional taxing authority he had requested or cut spending by that amount to balance the budget.

Barry was angered by several council members who criticized the mayor's revenue estimates as too conservative and suggested that revenues from current sources would be more than enough to balance next year's budget. Their skepticism was fueled by an audit showing that the city finished fiscal 1981 with a $68-million surplus, about $60 million more than Barry had predicted.

"I have no choice but to veto the entire budget unless they send me a balanced budget," the mayor said at the time. "You can't continue to have political rhetoric, adding here and adding there, without having the money to pay for it."

The council defied the mayor the next day by passing the budget, 10 to 4, without additional taxing authority. With seven of the 13 seats on the council up in this fall's election, members were in no mood to approve any tax increase, several members observed. However, the council did approve an amendment offered by Nadine P. Winter (D-Ward 6) to change the language of the report which described the mayor's request for additional taxes from "uncertain" to "pending."

Gladys W. Mack, the mayor's budget director, said shortly after the council meeting that the wording change failed to satisfy the mayor's objections. But yesterday, the mayor contradicted Mack, telling reporters that the wording change made a big difference.

"Legally, there's a great deal of difference between 'uncertain' and 'pending,' " Barry said.

"My legal advisers tell me that the council's agreement to include language about 'pending' revenue measures rather than 'uncertain' revenue satisfies both the legal requirements and my financial standards for a balanced budget," he added. "I'm convinced the council will pass additional taxes if necessary."

Barry declined to say whether he specifically asked Winter to introduce the amendment which ended up providing the justification for backing down from his veto threat. Winter told reporters that she developed the amendment on her own. However, several of her colleagues said it was a "common understanding" that Barry suggested it.

The mayor's office will transmit the budget to the Reagan administration later this month for review by the Office of Management and Budget (OMB), before it is formally submitted to Congress no later than April 15 for approval.

The council approved the broad outlines of the budget plan that Barry introduced last January. Barry, in turn, went along with several major council revisions, including spending $20.7 million more for the public schools and nearly $14 million less for debt retirement than the mayor had recommended.

In addition, the council also voted to keep open two fire stations in the near-downtown area of Ward 2 that Barry at one time wanted to close. The council also approved additional funds for two legal aid programs.

The mayor said yesterday he was disappointed that the council cut out the additional funds he requested to improve the city's financial management system, and contended that the $2.8 million set aside for debt retirement was not enough.