U.S.-Israeli friction over Israel's annexation of the Golan Heights increased today as Defense Minister Ariel Sharon bitterly accused the Reagan administration of intending to undermine Israel's national security.

In the first official Israeli response to the U.S. decision yesterday to suspend the two countries' new strategic cooperation agreement, Sharon said the move casts doubts on the credibility of the U.S. commitment to fulfill its obligations under the Camp David peace accords.

"In my opinion, the American steps announced yesterday raise doubts over American behavior in the future in connection with the implementation of the Camp David agreement," Sharon said in an interview on the state-run Israeli radio.

He added, "What makes the American punitive measures so serious is that they are intended to strike at Israel's national security, and how can Israel play a role in the security of the region if her own security is being undermined?"

Egyptian President Hosni Mubarak called the U.S. action "an encouraging decision" and said, "We hope in the light of what is going on now that reasonable solutions for this problem can be reached so that differences are not escalated further," Reuter reported from Cairo. Mubarak talked to reporters as the People's Assembly held an angry debate on the Israeli annexation. One delegate called for the withdrawal of the Egyptian ambassador from Tel Aviv in protest. The Arab League is to meet on the issue Monday in Tunis.

The stridency of the Israeli defense minister's remarks and their aggressive tone contrasted sharply with last night's taciturn reaction by officials of Prime Minister Menachem Begin's government.

Stunned by the U.S. suspension of the strategic cooperation accord and of a commitment to purchase $200 million worth of Israeli-manufactured arms, officials had said they would be unable to respond until the Cabinet met Sunday to weigh the implications of the U.S. move.

However, because Sharon personally supervised the strategic accord negotiations and signed the agreement in Washington with U.S. Defense Secretary Caspar W. Weinberger, he was said to have felt personally offended by the suspension.

Amid domestic criticism that there is less to the strategic agreement than meets the eye, and that it unnecessarily had placed Israel in a confrontational status with the Soviet Union, Sharon had defended the pact vigorously as essential to Israel's security.

In Washington last night, Ambassador Ephraim Evron also commented on the U.S. move, expressing "deep disappointment."

The Cabinet is to meet Sunday in Begin's home, where the prime minister is recuperating from a broken thigh, to draft a formal reply to the U.S. decision. Before the meeting, Begin is to meet with U.S. Ambassador Samuel Lewis.

Referring to the rapid parliamentary moves Begin engineered Monday to win approval of the annexation bill, Sharon said, "There is no reason for surprise by the Americans. Only the timing was surprising. The question of the Golan Heights is in the platform of the government, and I'm sure the Americans read every document in Israel, and they must have noticed this involved the intentions of this government."

Sharon said the strategic cooperation agreement pertains only to "forces outside the region" and has no bearing on Israel's position toward Arab neighbors. He argued that the provisions in the agreement requiring both the United States and Israel to take each other into account when taking unilateral action in the region was supposed to have pertained only to the threat of Soviet expansion.

"As for our defensive preparedness in the Golan Heights, we made it perfectly clear to all parties concerned, including the United States, that we have no intention of engaging in a military confrontation with the Syrians," Sharon said. "We will not hesitate to fight if we are attacked, but we are certainly not looking for a pretext to go to war."

That remark appeared to refer obliquely to Secretary of State Alexander M. Haig Jr.'s reported statement to Israeli Embassy officials in Washington that if Israel feels no compunction about annexing the occupied Golan Heights, the Americans have no assurance that it will not launch a unilateral military operation against Syria or Lebanon.

Also, Sharon appeared to be responding to criticism by opposition Labor Party Knesset member and former Army Chief of Staff Mordechai Gur that Sharon has been looking for an excuse to go to war with Syria.

Sharon added, "I am against war on any front, but particularly war on the Syrian front. Those who know me know that for many years . . . . I said that the last place in which Israel can expect any achievement, politically or militarily, in a war would be a war with Syria. We have no interest in such a war, and this was the basis of the government's policy in the past few years."

Sharon said the Egyptians also were not surprised by the Golan Heights annexation, because he repeatedly had told officials in Cairo that "under no circumstances will we go down from the Golan Heights."

Israeli radio later reported that 5,000 Israelis protested the annexation in Tel Aviv. The demonstrators carried placards reading, "Zionism yes, annexation no" and "We are not living in South America, stop the dictatorship now."