Spokesmen for President Carter acknowledged yesterday he had tried to delay Egyptian President Anwar Sadat's plans for a "Cairo summit" on the Arab-Israeli conflict, but insisted the only purpose was to improve the chances for the meeting's success.

White House press secretary Jody Powell insisted that Carter was "certainly not" trying to block the meeting when he suggested Sadat delay his announcement of the meeting and later proposed a postponement in the meeting date.

Powell and other administration spokesmen discussed the U.S. role in the Cairo talks, now slated to begin about Dec. 13, while confirming plans for Carter's trip to Europe, the Middle East and India at the end of this month.

The President will leave Dec. 29, and return Jan. 6 on a journey to Poland. Iran, India, Saudi Arabia and France , making up the substance of a tour he had originally scheduled for this time.But postponed because of the congressional impasse on energy legislation.

Officials said that three other countries which were on the original Carter itinrary - Brazil. Venezuela and Nigeria - will be visited by the President between March 24 and APril 3. Other countries may be added to that itinerary.

Powell also disclosed - apparently inadvertently - that the President will attend an economic summit meeting in Bonn later next year. That meeting is tentatively scheduled for June or July.

At his daily press briefing. Carter's spokesman went to unusual lenghts to rebut published speculation that despite the President's Wednesday press conference praise for Sadat's initiative, he hadactually been working to head off the Cairo conference.

Powell said that Carter had decided as soon as he learned of Sadat's plan that the United States would support it and attend the Cairo meeting.

He confirmed that the President had unsuccessfully suggested that Sadat delay announcing his plans, that Carter had ordered a delay in announceing the U.S. decision to attend, and that he had persuaded Sadat to delay the date of the meeting from early December to the middle of the month.

But in each case, Powell said, the President's motive was to improve the chances for success of the meeting and to try to persuade additional countries to attend.

"Our efforts were in support of the (Sadat) initialive," Powell said.

In the end, most of the invited countries refused Sadat's invitation, leaving the Cairo "summit" to Israel, Egypt, the United States and an observer from the United Nations.

But other government officials, endorsing Posell's version of administration policy, held out the hope that the Cairo talks could later be widened to include Jordan, "moderate Palestinians," and perhaps, eventually, Syria and the Soviet Union as well.

They spoke of a series of "concentric circles," expanding until almost all the parties the United States had been trying to draw into a Geneva conference on the Middle East were involved in the talks.

Powell said the President's strategy had been confirmed at two meetings on Monday with VIce President Mondale. Secretary of State Cyrus R. Vance and National Security Adviser Zbigniew Brzezinski. He said there were "no substantial or sharp differences of opinion expressed by any of the participants.