Australia's opposition Labor Party today reversed itself and agreed to support continued operation of a remote American military base where more than 1,000 U.S. technicians work.

The party's decision to join the ruling Conservative Party in backing the base's presence here came after opposition leader Bill Hayden disclosed that the base has no missile systems but is instead a monitoring station that is expected to be an important part of the network for verifying Soviet compliance with the SALT II agreement.

Hayden overcame opposition to the base from extreme leftists in his party by arguing that adoption of their position, which could have meant the closure of the base if Labor returns to power here, might hinder prospects for passage of the SALT treaty in Washington.

"The hawks in the American Congress will latch on to a decision to terminate these base arrangements as further grist to the mill of opposition to the SALT II agreement," he told the party's biennial conference in Adelaide.

The Labor Party's decision means that the base, located on more than one hundred square acres at Pine Gap in central Australia, will remain open regardless of changes of government here.

Hayden, 47, won the support of the party by a vote of 25-20. The victory, at Hayden's first conference as party leader, helped solidify his position as head of the socialist-oriented party.

Leftists in the party have been campaigning to have the base closed since it was built 10 years ago under the supervision of the U.S. Central Intelligence Agency. The base has been described as an Australian-American space research facility, but its exact purpose had not been publicly revealed until today.

The current government of Australia, headed by Prime Minister Malcolm Fraser, has been a warm and willing host to Pine Gap and other American bases. The Fraser government has another 18 months in power before it must call another election.

In his speech today, Hayden said, "Pine Gap is not part of any missile system. But its purposes are related to the SALT II verification processes.

"It is very important that we bear in mind what is the situation with SALT II, which is yet to be ratified by the U.S. Congress."

He said it would be a "painful paradox" if the Labor Party, "with its concern about international tension and conflict," took steps that could "subvert" the arms control agreement.

"If we were to adopt a hard line and make it obvious that the American bases were imperiled with the advent of a Labor government, we would be playing into the hands of the hawks in the American Congress," he added. "It is as simple as that."