The White House is likely to accept a ban on further testing of antisatellite weapons to avoid upsetting an agreement by House and Senate negotiators on increased spending levels for the Defense Department, congressional and administration sources said yesterday.

A miniconference on a catchall fiscal 1986 spending bill on Friday agreed to a higher-than-expected funding level for defense, but attached an amendment prohibiting use of funds in the bill "or any other act" for testing of antisatellite (ASAT) weapons.

The amendment was approved hours after the Air Force announced that it had launched two satellites as test targets. If the ban survives, the targets would orbit the Earth uselessly until at least the next fiscal year begins on Oct. 1, when the legislation would expire.

The Air Force said the inflatable balloon-like targets were launched at 9:35 p.m. Thursday from Wallops Island, Va. The miniconference, essentially a subcommittee of the full conference, was aware of the launch at the time it approved the amendment, participants said.

If the testing ban sticks, it could spell the end of the controversial, trouble-prone program that began in the late 1970s as a bargaining chip to negotiate an antisatellite agreement with the Soviets. When those talks failed, the Reagan administration decided to accelerate the U.S. antisatellite weapons program, arguing that the Soviets already had such a system.

Rep. George E. Brown Jr. (D-Calif.), a leader in the effort to halt antisatellite testing, predicted that the ban will be approved by Congress Monday. He said it "gives a little breathing space for the president if he wants to enter into real negotiations" with the Soviet Union.

"If the president is serious about a 50 percent cut in nuclear weapons," Brown said, "he will have to go for a limit on space weapons and an antisatellite moratorium is key to this."

While the conferees approved the antisatellite test ban sought by the Democratic-controlled House, most other controversial issues in the defense spending miniconference were settled in favor of the Senate.

Overall, the conferees approved $298.7 billion for the Pentagon in the current fiscal year, which ends next Sept. 30. That is close to the GOP-controlled Senate figure and includes $2.75 billion for President Reagan's Strategic Defense Initiative, the "Star Wars" research program.

The conferees also provided for resumption of chemical-weapons production, but with two provisos: that chemical artillery shells would not be built until 1987 and that the proposed chemical bomb would be delayed for further testing. All House provisions for procurement revisions were dropped at the insistence of the Senate conferees.

"The money approved by the conferees was better than expected," an aide to Reagan said yesterday, adding that the White House might not want to upset the total package to continue antisatellite tests. He also said the White House "was strongest in the miniconference" and that if calls from the president had not swayed that group, it was doubtful they could succeed in the larger conference Monday.

The ban would prohibit use of funds for testing an antisatellite weapon unless the president certifies that the Soviet Union has conducted such a test, according to a congressional aide who took part in the negotiations.

Language banning use of funds in "any other act" was added Friday after House negotiators learned that administration officials thought that test funds left over from last year could be used to carry out planned tests, the House aide said.

Two House conferees, Norman D. Dicks (D-Wash.) and Les AuCoin (D-Ore.), insisted on the added words after Sen. Ted Stevens (R-Alaska), chairman of the Senate Appropriations defense subcommittee, said he would accept the House-passed language banning tests with fiscal 1986 funds.

Brown said yesterday he hopes "by next year to have enough votes to abolish the program."

The antisatellite weapon is carried by an F15 fighter and launched at 40,000 feet. The rocket shoots a miniature homing vehicle into the path of the target satellite and destroys it on impact.

The first test against a target in space took place on Sept. 13 against an operating research satellite.