Members of the Senate Foreign Relations Committee put the Reagan administration on notice yesterday that U.S. aid to Pakistan is in serious jeopardy due to charges of Pakistani nuclear procurement in the United States, according to congressional sources.

The senatorial statements came in a closed-door meeting with Undersecretary of State Michael H. Armacost on the case of Arshad Z. Pervez, a Pakistani native arrested in Philadelphia July 10 on charges of seeking to illegally export sensitive U.S. materials for use in Pakistan's nuclear program.

Armacost, set to testify public- ly on the issue before a House

subcommittee today, is scheduled to go to Pakistan next week for what shapes up as important discussions.

State Department officials yesterday welcomed word from Pakistan that an arrest warrant has been issued for retired brigadier general Inam ul Haq, identified in court papers as a businessman from Lahore in northeast Pakistan who directed Pervez in his search for the sensitive nuclear-related materials.

While evidently far from sufficient to quell demands in Congress for a cutoff of aid to Pakistan or other strong action, the arrest warrant signifies that the Pakistani government is taking the situation seriously, officials said.

After the briefing with Armacost and with a U.S. Customs official working on the case, Sen. Claiborne Pell (D-R.I.), the Foreign Relations Committee's chairman, said Pervez has not yet been established to be an agent of the Pakistani government.

"It is my strong view that if not, he was acting with their knowledge," the Rhode Island Democrat said. He added that Pervez "may be proven to be" an agent of the Pakistani regime.

On April 23, the Senate Foreign Relations Committee in an 11-to-8 vote defeated a move by Pell and others to penalize Pakistan for nuclear-related activities by holding back $110 million of a planned $625 million aid program for fiscal year 1988 unless that country stops producing "weapons-grade nuclear material."

In a statement calling for an aid cutoff, Pell said yesterday, "Our record of accepting {Pakistan's} lies and transgressions has obviously sent a weak message . . . . "

The Foreign Relations Committee chairman declared, "Now is the time to show Pakistan we mean business."

Sens. John F. Kerry (D-Mass.) and Christopher J. Dodd (D-Conn.), who voted with committee Republicans in April not to penalize Pakistan, were both reported to be reconsidering their positions.

Kerry, through an aide, said that under these circumstances, the United States should follow existing law, which mandates a cutoff of aid to any country such as Pakistan seeking to illegally export nuclear-related material from the United States.

An aide to Dodd said the Connecticut Democrat will await Armacost's report after visiting Pakistan before deciding his position.

Making the administration position especially difficult, according to officials, is the fact that Congress must vote a special waiver of U.S. nonproliferation laws if the Pakistani aid program is to continue past Sept. 30.