The Reagan administration yesterday defended its controversial proposal to lift the ban on covert or overt assistance to rebel forces in Angola, amid reports that a senior administration emissary has met secretly with the leading figure in the insurgency.

State Department spokesman William Dyess said the administration decided to ask Congress to repeal the 1976 prohibition on Angolan rebel aid because it is "an unusually all-encompassing restriction on U.S. policy options."

Dyess said it would be a mistake to draw conclusions from this decision regarding future administration policy in Africa. The policy is under intensive review.

The spokesman went on to say that "we are engaged in consultations with all the interested parties" about the U.S. policy review.

Dyess was unable to say whether the administration, in this connection, has been in touch with Jonas Savimbi, the leader of UNITA, a rebel faction formerly backed by the CIA in Angola. Other sources said Savimbi met a U.S. emissary in Morocco about a week ago.

Leonard R. Sussman, executive director of Freedom House, said the New York -based Private organization expects to host a visit here by Savimbi sometime in the next several weeks. Freedom House was the sponsor of a similar tour by the unsurgent leader in late 1979.

In an appearance before the House Budget Committee yesterday, Gen. David C. Jones, chairman of the Joint Chiefs of Staff, spoke for repeal of the prohibition on aid to the Angolan insurgents. That restriction, he said, gave the Soviets and Cubans "a free ride" in Africa.

"It gave them a free ride in Angola and then in Ethopia, and now they are encroaching on our part of the world," said jones, apparently referring to Central America.

African leaders have warned that U.S. support of rebel forces against an accepted government, such as that in Angola, would have powerful repercussions on U.S.-African relations.

Several European foreign ministers who recently visited Washington urged the Reagan administration to back diplomatic rather than military solutions to African problems, and especially to back continuation of western-sponsored negotiations regarding Namibia, which borders Angola.

Several members of Congress, including the chairman of the Africa subcommittees of the Senate and House, have raised particular objections to the timing of the administration's drive to lift the ban on aid to Angolan rebels.

The lawmakers argued that, in advance of the conclusion of the broader policy review, such action would send an unnecessary and unwelcomed signal of a future policy that is repugnant to many African nations.

The argument within the administration, according to informed sources, was that the request for lifting the ban was timely, to let everyone know the new administration would resist any such restrictions.

The administration's senior African specialists reportedly took the view that the congressional drive could be satisfactorily explained to the nations of the continent.

Dyess said that in the policy consultations now in progress, "we are making clear our firm intention to seek viable diplomatic solutions to the problems of southern Africa." However, a senior State Department official said this did not necessarily mean that the United States will continue its support for the Namibian negotiations.

According to informed officials, the United States has not yet been in direct consultation with the Angolan government, which reportedly has expressed an intention to send Cuban military forces home if Angola is no longer threatened by South Africa military forces based in Namibia.

The United States does not recognize the Angolan regime.

During his election campaign, President Reagan said he favored providing arms to Savimbi. Reagan said in an interview that The Wall Street Journal last May 6 that Savimbi "controls more than half of Angola" and had "never asked for any kind of help except weapons."

"I don't see anything wrong with someone who wants to free themselves from the rule of an outside power, which is Cubans and East Germans -- I don't see why we shouldn't provide them with the weapons to do it."

In a related development, the State Department confirmed that U.S. food aid to Mozambique has been suspended, apparently in retalliation for the recent expulsion of four American embassy personnel accused of espionage.

The interrupted aid includes about $5 million worth of wheat and rice, plus 27,000 tons of corn awaiting shipment.