The United States' next moves against Iran are likely to involve new political and economic measures, and not a military operation such as a naval blockade, White House press secretary Judy Powell said yesterday.

Seeking to dampen speculation that President Carter is nearing the point or ordering last-resort military measures to end the Iranian crisis, Powell told reporters, "You should not assume that nonviolent military action [a blockade] is the next step or that these [military steps] are the only options available to us."

He said that while Carter has made no final decisions on what steps he will order next if the stalemate continues, the president has "a pretty good idea" of what they will be, and they involve additional political and economic pressure on Iran.

Powell refused to detail what measures are being considered by the administration or to indicate how long Carter will wait before imposing them.

Yesterday, the administration clamped new restrictions on the few Iranian diplomats who remain in the United States. It barred Iran's 12-member delegation to the United Nations and members of the diplomats' families from traveling more than 25 miles from New York City without special permission.

Similar travel restrictions are in effect against Cuban and Albanian diplomats, and have been imposed on other nation's U.N. representatives in the past.

Powell's comments about additional political and economic options still available to Carter in the Iranian crisis appeared to be a deliberate attempt to cool some of the rhetoric and tension that followed Carter's announcement Monday that the United States was breaking diplomatic relations with Iran and would impose new economic sanctions on that country.

The United States is now appealing to its allies to join in inceasing the political and economic pressure on Iran, giving rise to the impression that if such unilateral or joint measures fail to win release of the American hostages in Tehran, military steps by the United States would become inevitable.

The Iranian militants who hold the hostages responded to the break in diplomatic relations and the new economic sanctions by threatening to kill their captives if the United States makes any military moves.

The administration has held open the possibility of using military force to end the crisis since shortly after the Nov. 4 takeover of the U.S. Embassy in Tehran. Carter reiterated that threat as recently as Thursday, when he told the American Society of Newspaper Editors convention here: "We will pursue every -- and I repeat, every -- legal use of our power to bring our people home, free and safe."

But while these and similar statements focused attention on a military resolution of the crisis, Powell suggested yesterday that the administration hopes to keep the Iranian militants off balance in trying to anticipate the next American moves.

"The judgment is that it is better to let them think about it," he said.

Suggestions that the United States is nearing the point of taking military action might also alarm American allies, who are being asked by the administration to increase their political and economic pressure on Iran.

Powell and other administration officials yesterday continued publicly to express patience with the allies, who thus far have declined to go along with the kind of stringent political and economic steps Carter is seeking. Powell and others stressed that it will "take time" before the allies settle on a response to the American plea, and that the few steps taken by some allies since Monday have been in the right direction.

Powell also said that the next political and economic steps the president has in mind "would have an impact" even if they were not accompanied by similar action by the allies.

Carter yesterday renewed his appeal for help from the allies during a meeting with Dietrich Strobbe, the governing mayor of West Berlin.

"It's obvious the deep concern we have about Iran and the Soviet invasion of Afghanistan," the president said. "It's extremely important for all of us, in Europe and here, particularly in Berlin, to understand the extreme importance to us of a very close alliance and a very close understanding."

Strobbe replied, "I will do my best . . . to tell people in my country what you are thinking about the solutions we should try.