A high-level U.S. team flying to Algiers last night is prepared to warn Iran that U.S. government flexibility on the settlement of the hostage issue may expire next month with the Carter administration, official sources said last night.

The team, headed by Deputy Secretary of State Warren Christopher, is carrying the latest U.S. response to Iran's conditions for release of the 52 American hostages.

The U.S. officials are reported ready to make the point that "it will be a whole new ball game after Jan. 20" and possibly one less susceptible to accommodation with Iran's conditions.

President-elect Ronald Reagan speaking briefly to reporters in Los Angeles yesterday, seemed to hint at a similar message by saying it would be "pretty foolish" for Iran to wait for his administration to make a hostage settlement. Aides to Reagan have been informed of the positions being presented by the Christopher team, according to the sources.

Reagan was responding to questions generated in an interview Sunday by CBS News correspondent Mike Wallace with Ali Reza Nobari, governor of the Iranian Central Bank. Nobari suggested that Reagan as president might be able to grant greater concessions on the hostage issues than President Carter.

The new American message to Iran, to be conveyed through Algerian diplomats, was characterized by State Department officials as the next step in a potentially lengthy and tedious process of indirect negotiations with Tehran authorities. The U.S. officials emphasized that no immediate breakthrough is in sight for an end to the Americans' captivity, which began 13 months ago this week.

Christopher and essentially the same American team, including senior financial and legal experts, were in Algiers Nov. 9-12 to convey the first American response to the four conditions adopted by the Iranian parliament for release of the Americans. A three-member Algerian delegation took that U.S. message to Tehran. A week ago the Algerians flew to Washington with Iran's reply, which was essentially a request for further details and clarifications of the American position.

The nature and tone of the Iranian reply did nothing to assure American officials that a resolution of the hostage issue is possible through the current quasi negotiations. Rather than seeking a face saving way to confirm agreement between Tehran and Washington on the broad principles of the Iranian demands while glossing over problems of implementation, the Iranians have dug deeper into the nettlesome details with no hint of flexibility in their announced conditions.

The U.S. message that Christopher carried last night was described by informed sources as representing no change in the basic American position as previously set forth. In this sense the latest American response is not a counteroffer to Iran but a more detailed reiteration of earlier proposals, including the reported U.S. willingness to place claims and assets questions before third parties, possibly an international commission.

It remains to be seen whether this will be enough for the Iranians, who seem to be bidding for concessions that will bring the American position more closely in line with the letter as well as the spirit of the conditions adopted by the Majlis, Iran's parliament. About the best that could be envisioned yesterday by U.S. officials familiar with the closely held details of the international maneuvering was that Iranian authorities will see in the latest message from Washington the basis for further back-and-forth on the points at issue.

In this perspective, the Iranian deliberations on the new U.S. message, which the Algerians are expected to forward to Tehran later this week, are less likely to be conclusive about the immediate future of the hostages than about the immediate future of the process of the indirect discussions of the last month.

The four Iranian conditions call for the United States to pledge not to interfere in Iran's internal affairs, to release blocked Iranian assets in the United States, to remove legal claims filed against Iran in U.S. courts, and to send to Iran the wealth of the late shah and his family. According to Washington sources, the request for clarification received from Iran last week contained detailed questions about the U.S. position on all four points.

The State Department's announcement on Christopher's departure said there is no fixed return date. The expectation here is that his party will stay only a day or two in the Algerian capital before returning to Washington to await Iran's next move.