NORTH PLATTE, NEB., AUG. 13 -- President Reagan, heading west for a vacation at his ranch, said here today that peace and democracy in Central America is his "first order of business," and a senior White House official said the administration might seek renewed military aid for the Nicaraguan contras as "an insurance policy" for the peace process now in motion.

Speaking with reporters on Air Force One, the senior official said the Reagan administration is concerned about the period between Sept. 30, when U.S. aid to the contras will expire, and Nov. 7, the target date for a cease-fire under the peace plan agreed to last week by five Central American governments, including Nicaragua.

"We're going to have to address that interregnum," the official said. "We plan to address the funding issue in a way that will ensure that support for the contras continues until we are all satisfied that there is a peace plan that will ensure the peaceful reintegration and democratization of Nicaragua."

National security adviser Frank C. Carlucci said support "will continue until . . . there is a satisfactory nexus with the peace plan that puts in place democratic reforms."

On Air Force One, after leaving here, White House spokesman Marlin Fitzwater was asked about Carlucci's comment and said, "We won't desert the contras. We will make a decision by Sept. 30. We'll wait and see where we are on or about Sept. 30."

House Speaker Jim Wright (D-Tex.), who joined with Reagan last week in pushing a U.S. peace plan for Central America, could not be reached for comment on the administration official's remarks. But a House Democratic leadership aide said any White House request for contra aid while the peace effort is under way would violate the speaker's agreement with Reagan.

"We believe they are proceeding in good faith, and we are not inclined to get into a confrontation," said the aide. But he said if the administration does submit a funding request during the ongoing peace process, it would "be overwhelmingly defeated," as House members would rally behind Wright.

The Central American issue appeared to be foremost on the White House agenda as Reagan sought to put the Iran-contra affair in the past tense and move ahead to other issues. Heading west for a 25-day vacation in California, the president stopped off here to make two speeches in which he also urged approval of a constitutional amendment requiring a balanced budget and the confirmation of Supreme Court nominee Robert H. Bork.

{The president arrived safely in Santa Barbara, Calif., tonight after his helicopter was involved in a near-collision.}

Reagan limited the Iran-contra scandal to a single passage in his second speech, in which he told an enthusiastic crowd in the Buffalo Bill Wild West Arena that "my first priority was always to get the facts before the American people."

Now, the president continued, "it's time to get down to the real business at hand: to move forward with America."

In a nationally televised address from the Oval Office on Wednesday night Reagan shouldered responsibility for the Iran-contra affair and said aides should not have shielded him from making a decision on whether proceeds from the arms sales should be diverted to aid the contras. He did not say what his decision would have been, although his spokesmen have claimed that he would have vetoed the diversion.

Today, senior White House officials said that the president intends to move beyond the Iran-contra affair to other issues.

"My view is {that} the president has done about all he can now," national security adviser Carlucci said on Air Force One. "He's accepted responsibility, said there are mistakes, cooperated with four committees. He's changed the people and he's changed the procedures."

Fitzwater said that Reagan "feels very positive" about the public response to his speech and that telephoned responses were overwhelmingly favorable. He said the American people "want the president to lead and succeed, and he will."

An ABC News poll conducted Wednesday night showed that Americans want to move on to other issues but remain uncertain and suspicious of Reagan's role in the Iran-contra affair.

Today, Reagan called for an end to the fighting in Nicaragua and "a commitment to democratic reforms by the Sandinista communist government." He said the reforms must include free elections, restoration of a free press and other civil rights and demilitarization.

Some conservatives, including presidential aspirant Rep. Jack Kemp (R-N.Y.) today, have accused Reagan of preparing to turn his back on the contras, and today's remarks by White House officials appeared intended as reassurance that Reagan would not abandon them unless democracy has been restored in Nicaragua -- the proclaimed goal of the contra insurgency. In his Wednesday speech, Reagan said he remained committed to "the democratic resistance -- the freedom fighters -- and their pursuit of democracy in Nicaragua."

Carlucci said that nothing in an agreement reached last week by Reagan and Wright prevents the administration from seeking interim funds for the contras while peace negotiations are pending.

In Washington, the State Department spokesman Charles E. Redman rebuffed a call by Nicaraguan Foreign Minister Miguel d'Escoto for the administration to cut off aid to the contras immediately. He said the Sandanistas created the problems because of their repression and said "true democracy guaranteeing Nicaraguans' political and civil liberties would bring an end to the armed struggle."

The president also repeated his determination to fight hard for the confirmation of Bork, who has been depicted as a conservative judicial activist by liberal groups seeking to keep him off the high court.

Following the White House strategy of emphasizing Bork's undisputed legal credentials and playing down his ideology, Reagan called Bork "a jurist of outstanding intellect and unrivaled qualifications, a brilliant legal scholar and a premier constitutional authority."

In a luncheon speech to Nebraska civic leaders and politicians, Reagan emphasized the importance of keeping foreign markets open to U.S. farm products and hinted he would veto pending trade legislation he said was the work of "protectionists."

The president was greeted today by friendly crowds in an area where he received nearly four-fifths of the vote in 1984. Signs in the western-garbed crowd proclaimed, "The Wild Bunch Rides With Ronnie" and "Bridle the Budget, Gipper."

The ABC poll showed that Americans want to move on to other issues besides the Iran-contra affair. About four out of five respondents to the telephone survey, regardless of whether they heard the speech, agreed with the statement that it is "time for the country to put the Iran-contra hearings behind us."

Of the 177 people who had heard the speech, about three of five said Reagan generally told the truth about his involvement in the scandal. But about half said they were dissatisfied with his explanations.

Less than one out of five said that Reagan had answered "most questions" about his role. Nearly two out of five said he "answered very few questions" in his broadcast address to the nation. Freed Hostage Jenco Calls Iran Affair 'Morally Wrong' Associated Press

PITTSBURGH, Aug. 13 -- The Rev. Martin Jenco, a former hostage in Lebanon who was released during the time the United States was selling arms to Iran, said today President Reagan's admission that the Iran-contra affair was a mistake is not enough.

"It was morally wrong," Jenco, 52, told 200 representatives of Roman Catholic religious orders in the United States.

"Apparently, the president and I have a different definition of the word mistake," he said.

Jenco was freed in July 1986, two months after a trip to Tehran by former national security adviser Robert C. McFarlane and in the midst of American arms sales to Iran. Jenco said he would rather have died than be traded for weapons.

"The release of one hostage to send over instruments of war to kill millions of children. . . one should worry about that. It wasn't just a mistake. It was wrong," he said.