Despite pleas from legislators, domestic industrialists and foreign allies, President Reagan is sticking firmly to his refusal to export U.S. technology to the Soviets for construction of a natural gas pipeline to Western Europe.

"There's no way in the world the president's going to change his mind on this one," a high-ranking White House official said yesterday hours after a delegation of Illinois lawmakers and industrialists, led by Senate Foreign Relations Committee Chairman Charles H. Percy (R-Ill.), met with national security adviser William P. Clark in an effort to persuade Reagan to lift the sanctions.

Though Clark promised to convey the delegation's views to the president, officials said later that Reagan would not back away from his tough anti-Soviet stand.

The promptness of this response underscored Reagan's unwillingness to compromise even though some administration officials -- including Secretary of State Alexander M. Haig Jr. and Secretary of Commerce Malcolm Baldrige--have expressed reservations that the policy is damaging U.S. policy at home and abroad.

Percy's plea was the latest in a series of attempts to persuade the president to lift or modify the sanctions he imposed Dec. 29 and toughened June 18 in an effort to raise the level of U.S. pressure against the Soviets in retaliation for continued repression in Poland.

On Wednesday the president heard a similar appeal from British Prime Minister Margaret Thatcher, who told him that the sanctions were harming a Scottish-based British company.

Reagan's reply, according to administration officials, was that the sanctions were a necessary response to the Soviet actions and that he intended to continue them. Thatcher, who would like the United States to continue its sanctions against Argentina, imposed after the Falklands invasion, reportedly did not press the point.

The president's June 18 action toughening the Soviet sanctions--a move that came after a National Security Council meeting in which both Secretary of Defense Caspar W. Weinberger and White House counselor Edwin Meese III argued in favor of the sanctions--extended the Dec. 29 ban on the sale of U.S. oil and gas equipment to include overseas subsidiaries of U.S. firms and non-American firms producing equipment under U.S. licenses.

It is this extension that has produced expressions of concern in West Germany, Britain, France and Italy that the president is backing away from implied promises given to allied leaders during Reagan's recent European trip.

Yesterday, Percy said that the president's action would cost tens of thousands of U.S. jobs during a recession and create "a crisis in the western world" without delaying the pipeline.

This argument has not impressed Reagan, who is said to have come to the conclusion that the United States would appear weak and indecisive if it gave up the sanctions at the same time the Russians show no sign of moderating their conduct in Poland and Afghanistan.

The only way Reagan's view is likely to change, in the opinion of those close to him, is if the Soviets adopt a more benign position, particularly in Poland. The president has expressed the view that his firm stance is in the long-range interests of the West, including those European allies who are opposed to his view.

As a result, say those who are close to Reagan, the fate of the sanctions will depend not on on the words of protest of a senator or foreign ally but on the actual conduct of the Soviets.