The Reagan administration is asking Pakistan to reduce the efficiency of its uranium enrichment plant and permit outside inspection to ease the U.S.-Pakistani confrontation over nuclear weapons proliferation, administration officials said yesterday.

The U.S. proposal is part of the "concrete evidence of Pakistani nuclear restraint" that Assistant Secretary of State Richard W. Murphy listed as a central U.S. objective in testimony yesterday before two House Foreign Affairs subcommittees.

The outcome of the confrontation, brought on by the arrest of a Pakistani native July 10 on charges of seeking to illegally export U.S. material for Pakistan's nuclear weapons program, will depend "to a very large degree on Pakistan's response" in the days ahead, Murphy said. He emphasized that under present circumstances, Pakistani verbal assurances "must be matched by their actions."

The functioning of Pakistan's uranium enrichment plant operations is pertinent because the steel allegedly sought for illegal export from the United States is believed to have been destined for this purpose.

After a letter from President Reagan in late 1984, Pakistan promised the administration not to enrich uranium at a higher lever than about 5 percent, which is adequate for civilian power programs but not for making bombs. However, U.S. intelligence reports indicate that the enrichment level at Pakistan's Kahuta plant near Islamabad has reached weapons grade of more than 90 percent.

The administration is asking, sources said, that Pakistan retool its plant so that future enrichment would be about 5 percent and permit outside inspection to determine that changes had been made. This would leave a certain amount of nuclear material, already produced, that could be used for weapons, but probably only enough for a few bombs, according to U.S. experts.

If such an enrichment limit were accepted for the future, it could help to forestall escalation by India of a threatened South Asian nuclear arms race. Some sort of Indian cooperation is also being sought, Murphy said in his testimony.

Shortly before Murphy testified, House Foreign Affairs Committee Chairman Dante B. Fascell (D-Fla.) released a letter to Reagan urging him to temporarily suspend U.S. military and economic assistance to Pakistan pending discussions and a reassessment of the nuclear situation.

Pakistan has denied any connection with the activities of Arshad Z. Pervez, being held in Philadelphia on federal illegal export charges. But Rep. Stephen J. Solarz, chairman of the Asian and Pacific Affairs subcommittee, said that the information received so far suggests that the authorities in Islamabad knew about the planned exports.

Pakistan has issued an arrest warrant for Inam ul Haq, who was named as the man directing the procurement effort from Lahore. But the State Department said yesterday he has "disappeared."

A 1985 law sponsored by Solarz calls for a cutoff of U.S. aid to a country without nuclear weapons, such as Pakistan, which seeks to illegally obtain nuclear-related material from the United States. Solarz said the law must be enforced unless there is "some agreement with Islamabad that would give us confidence that Pakistan is not producing highly enriched uranium."

Rep. Jim Leach (R-Iowa), the ranking minority member of Solarz's subcommittee, cautioned that cutting off all U.S. aid "may endanger Western security and the Afghan resistance" and cause Pakistan to move quickly toward nuclear weapons production.