SANTA BARBARA, CALIF., AUG. 14 -- The White House, concerned about confusion over administration efforts to encourage the peace process in Central America, today reassured House Speaker Jim Wright (D-Tex.) that President Reagan will not request more military or humanitarian assistance for the Nicaraguan contras before Sept. 30, senior administration officials said.

But as the White House worked to calm congressional Democrats, another problem arose when Reagan's special envoy for Central America, Philip C. Habib, announced his resignation in Washington.

State Department and congressional sources said Habib acted after his call for immediate, high-level U.S. involvement in peace talks between Nicaragua and its Central American neighbors was rejected by the administration. {Details, Page A14.}

Today's events underscored the conflicting pressures buffeting Reagan's new Central American policy and highlighted the unease inside the administration over the peace plan hammered out last week by the countries in the region. Top administration policy-makers are concerned that aspects of the Central American plan may be contrary to U.S. interests because they don't do enough to end Soviet and Cuban influence in the region. The Central American plan differs in key respects from one proposed by Reagan and Wright.

It was in part because of those differences that administration officials suggested Thursday that Reagan might sometime next month seek renewed aid for the contras fighting the government of Nicaragua. But this morning, national security adviser Frank C. Carlucci telephoned Wright and Rep. Tony Coelho (D-Calif.) and pledged that any request for additional aid would be delayed at least until Sept. 30 under terms of an agreement between Reagan and Wright, according to administration officials.

The officials emphasized, as did White House spokesman Marlin Fitzwater, that what happens after that date depends entirely "on the process of democratization" in Nicaragua.

In Washington, Coelho and Wilson Morris, a spokesman for Wright, said Wright is satisfied. "We have been assured that their aim is to go all-out for the peace proposal and that there will be no aid request through the end of September," Morris said. "Any further aid will be subject to discussion."

Morris said Wright "wasn't pleased" by reports of a new contra-aid request but added, "We think everybody is still acting in good faith."

Carlucci's reassurance came after a day of confusion in which comments by some White House officials, including Carlucci, were interpreted as reflecting Reagan's determination to request further contra aid.

The current appropriation of $100 million for the contras expires Sept. 30, while a cease-fire in the Nicaraguan civil war is not scheduled before Nov. 7, according to last week's plan by five Central American countries, including Nicaragua.

As Reagan headed west Thursday, Fitzwater assured reporters, "We won't desert the contras," and Carlucci and White House chief of staff Howard H. Baker Jr. said they were especially concerned about the period between Sept. 30 and Nov. 7.

Coelho attributed the White House statements on contra aid to pressure from conservative groups opposing the Central American peace proposal by Reagan and Wright.

"They are getting a tremendous amount of pressure from the right wing," Coelho said. "At some point, the White House is going to have to decide whether it is going to work with the right wing or work for peace . . . . Obviously, people from the right wing are trying desperately to get {the plan} off track."

But, Coelho added, "We have no indication from our conversations with Baker and Carlucci that they are moving away from their position."

Today, White House officials said the conflicting signals reflected administration responses to conflicting pressures.

"Conservatives are worried that the president will abandon the contras, while liberals are concerned that he is not serious about a peace plan," a senior White House official said. "We're trying to walk a middle ground."

Another official said Reagan is "under heavy pressure from his own right wing." A group of conservatives, many of them longtime Reagan supporters, met with Reagan in the White House before his vacation and urged him to reaffirm support for the contras.

The pressure on Reagan continued Wednesday when Rep. Jack Kemp (R-N.Y.) called the Central American peace proposal "a dead end for freedom" and urged Reagan to submit a new request to Congress for at least $210 million in military aid for the contras.

Fitzwater reflected on the conflicting pressures as he briefed reporters today, saying that "the conservative leadership in this country have very strong feelings, liberal Democrats have very strong feelings . . . . there are also strong pressures coming out of Central America."

He added that "the president is the anchor in this and his position has been the same from the beginning, and that is that the Wright-Reagan plan represents the principles that we believe in and are important for peace in Central America."

The Central American countries rejected this plan last week in Guatemala City and adopted a Costa Rican proposal that differs in several important respects.

The most important difference, from the White House point of view, is that the Wright-Reagan plan would require the Nicaraguan government to show evidence of democratization by Sept. 30.

Fitzwater said today that the administration does not favor one peace plan over the other "because we don't believe that either one of them represents a document that has to be stuck to or confined to in any sense. They both represent negotiating positions, a starting point . . . . "

Any final agreement is likely to differ from both plans, he said.

Officials who responded to questions today under condition that they not be identified stressed repeatedly that no decisions have been made on a contra aid request. One official said no request may be necessary if the newspaper "La Prensa is publishing, the churches are open and democratic reforms are being put in place."

He also said options for aid include renewed humanitarian assistance while the peace plan is being implemented and a provision for delaying military aid until the Sandinistas show sincerity.

Another official stressed that Reagan is aware of the "harsh realities" of the situation, which he said include likely congressional reluctance to approve further military aid for the contras.

"The situation is very fluid," this official said. "We'll start talking about this with Congress when they and the president return next month, but no decision on aid is imminent."

Coelho said congressional Democrats have determined -- and apparently persuaded administration officials -- that there will be "plenty of money left" from the $100 million Congress provided in the current fiscal year (which ends Sept. 30) to support the contras through November.

He said this assessment is based on "our contacts with audit and budget experts in the area."

The White House agreement with Wright includes no assurances that new contra aid will not be sought after Sept. 30. But Coelho said that, if peace negotiations appear to be progressing, a new aid request "would not pass."

"If things are going well on Oct. 1, even if there is no cease-fire but it is in prospect, I don't see a new military aid request coming up here," Morris said. "It would be counterproductive. The vote would be pretty clear." Staff writer Edward Walsh contributed to this report from Washington.