Sen. Jacob K. Javits (R.N.Y.) proposed yesterday that the North Atlantic Treaty Organization be asked to expand its area of responsibility to protect oil supply routes in the Middle East.

Lead-off witness at the first of a series of Republican platform hearings, Javits said that problems in Iran, Soviet aggression in Afghanistan and other potential dangers to Mideast oil make it imperative that NATO abandon its longstanding opposition to enlarging its area of responsibility beyond the North Atlantic and Western Europe.

"Our allies must stand up to this responsibility with us," said Javits, senior Republican on the Senate Foreign Relations Committee. "To do otherwise is to risk the collapse of NATO by the cutoff of its essential oil supply."

Rep. William S. Broomfield (R-Mich.), senior Republican on the House Foreign Affairs Committee, made much the same point at an afternoon session when he quoted approvingly a proposal that the United States should team up with 10 to 20 of its allies to "protect the sea lanes linking the great trading nations of the free world together with the most important suppliers of raw material resources . . . Control of the world sea lanes is a Soviet obsession."

Republican panels will hold hearings in nine cities during the next five months seeking public advice on what to include in their party platform.

Yesterday's session in the Senate caucus room heard members of Congress and former executive branch officials on a broad range of domestic and foreign issues.

The testimony will be taken to Detroit in July when the Republican National Convention will nominate its candidate for president and adopt a platform of policy positions that is supposed to tell voters when the nominee believes and will try to do if elected.

Carla Hills, last Republican secretary of housing and urban development, told the panel that ever-expanding government threatens productive capacity.

She recommended decentralizing policymaking by moving it out of Washington and back to the states and localities, greater involvement of the private sector in solving problems, more effective management of government activities and focusing government aid on special needs rather than trying to solve all problems with federal money.

Robert Bork, former solicitor general and briefly attorney general, said the presidency has been weakened by unconstitional acts of Congress. He cited the war powers act, which was a post-Vietnam attempt to prevent future presidents from taking the country to war without congressional approval. He also called congressional vetoes of executive branch regulations an invalid reversal of the constitutional process for permitting Congress to legislate and the president to veto.

James Buckley, a former New York senator now running in Connecticut, said Democrats have undermined the federal system created by the Constitution by moving government to Washington. Republicans should pledge to move it back to the states, he said, by handing out block grants of federal money with no strings attached.

Rep. Jack Kemp (R-N.Y.) said a Republican president should aim at reducing income tax rates by 40 to 50 percent in his first term and to reduce the maximum individual tax rate to 25 percent by the end of his second term. Lower taxes would stimulate the economy and bring in more revenue to finance worthy federal programs, he said.

Rep. Marjorie S. Holt (R-Md.) made a plea for adopting zero-base budgeting which she said President Carter promised but never produced. Sen. Larry Pressler (R-S.D.), who was running for president until last week when he decided he wasn't going to make it, made a plea for a big gasohol program. Carter announced his own last week.

Rep. S. William Green (R-N.Y.), who won the Manhattan seat formerly held by Democrat Bella Abzug, pleaded with his party to support urban programs. "If Republicans vote for the cities, the cities will vote Republican," he said.

A second round of hearings will be held in the Senate caucus room today.