The Carter administration and the government of Israel continued to clash yesterday over Middle East policy even though Egypt and Israel have agreed in principle to resume negotiations on the stalled Palestinian issue at the request of President Carter.

The latest clash had a special tone of bitterness as Israeli officials reacted with surprise and sarcasm to news that the administration had made an unsolicited offer of medical aid to the two Palestinian mayors crippled last week in bombings in the Israeli-occupied West Bank.

State Department spokesman Thomas Reston said the United States had let the doctors and the families of Nablus Mayor Bassam Al-Shaka, who lost both legs and Ramallah Mayor Karim Khalef, who lost a foot, know of "our willingness to supply whatever expertise and help we can to make their swift recovery possible."

Reston said the offer was made after the department learned that one of the families was "looking into" U.S. assistance, though no request for such help was made. He said it was done for humanitarian reasons, rejecting suggestions by Israeli journalists that it was politically motivated.

Privately, however, U.S. officials acknowledged that political considerations were involved.

An Israeli embassy official later expressed "surprise that the administration did not show the same concern and initiative, and invite for medical treatment" an Israeli policeman who was blinded when defusing a bomb in another mayor's car or Israeli children wounded in a terrorist attack last month.

"It would seem," the official said, "that these innocent victims of terrorism are entitled to the same degree of concern that was shown to the two mayors who are notorious supporters of the Palestine Liberation Organization."

The two Palestinian mayors may not wish to be treated in Israeli hospitals. Officials suspect the bombings were the work of Israeli extremists.

In another rebuke of Israeli policy on settlements in the West Bank, Reston said the United States "opposes any unilateral step on existing settlements or new settlements that undercuts" the Palestinian autonomy negotiations.

While the United States previously has used this terminology to oppose the 10 new settlements the Israeli government is going ahead with, Reston also used this language when asked about Prime Minister Menachem Begin's intention to "strengthen the population" in other settlements.