The District of Columbia government and the union representing the police have reached agreement on a three-year contract, city labor relations director Donald Weinberg said yesterday.

He declined to divulge its contents, but police sources said the agreement calls for lumps-sum "bonus" payments totaling $4,700 for about 3,300 police officers sergeant or below instead of salary increases for the first two year.

In the third year, the officers would get a cost-of-living increase between 4 percent and 9 percent of their current salaries, according to police who had been briefed on the agreement.

The estimated 300 officers above the rank of sergeant would receive only the third-year pay boost and nothing the first two years, the sources said.

Because the bonus payments the first two years will not be added to the officers' current salaries for calculating either the third-year pay increase or retirement pay, the terms immediately aroused strong opposition from some of the department's rank and file.

As the first agreement negotiated under the District's complex new Merit Personnel Act, which requires the home-rule government for the first time to bargain over wages and working conditions with all employes, the accord represents a legal and poltical landmark.

The city, in the midst of a financial crisis and with little money for pay increases the next three years, is expected to try to use it as a precedent for negotiations this summer with 14 other groups of workers.

But the agreement, accepted by the International Brotherhood of Police Officers [IBPO] as the official bargaining representative of the police, was immediately challenged by a rival union, the Fraternal Order of Police.

FOP leaders called it a "sellout," and they filed a formal petition with the city's Public Employe Relations Board seeking a new union representation election.

Executives of the IBPO, who declined to comment on the agreement yesterday, met last night at a downtown hotel to discuss procedures for ratifying the agreement. The union constitution does not require the contract to be ratified by members, but the union has decided to submit it anyway.

Weinberg said a formal announcement that the agreement had been reached, but not its details, would be made at a District Building press conference this morning. He said the contract had been approved by Mayor Marion Barry and City Administrator Elijah B. Rogers, and that the District government, despite chronic deficits and cash shortages, has enough money to pay for it.

"I don't bargain things I can't afford," he said.

Achieving "moderate" salary agreements with some 30,000 city workers and teachers is a key component of Barry's program to restore the District government's fiscal stability.

His budget for the 1982 fiscal year, the first year of the labor contracts being negotiated, contains only enough money to give workers a 2 percent pay increase. And so far the mayor has not identified any source of funds to finance additional increases in future years. i

The lump sum payments reportedly accepted by police negotiators would be considerably less costly for the city than cost-of-living increases based on a percentage of salary.

But for the same reason, they are expected to be less popular with the rank and file, police officers said yesterday.

Weinberg would not confirm the bonus payment arrangement; he said only that the agreement contains "some base pay" and some other forms of payment. He did say the contract also contains "some provisions on union security," that is, some arrangement by which the District would reinforce the position of the IBPO as authorized representative of the police.

Police sources said the contract also provides a substantial increase in health care benefits and hospitalization coverage for illnesses and accidents that are not job-related. The cost of the wage and benefits package could not be immediately determined.

Announcement of the agreement came as a surprise because the last news from the negotiations was that they had broken down in angry disagreement. IPBO negotitors walked out of the talks last month, declared them at an impasse and set in motion the machinery to go to arbitration.

Weinberg countered with an unfair labor practice charge against the union.

Weinberg said "it would have been silly" to accept the breakdown as irreversible, and that talks had continued even during when they were officially suspended.