The Reagan administration today applauded Japanese Prime Minister Yasuhiro Nakasone for his efforts to expand imports from the United States, but said more needs to be done.

Critics of Japan said Nakasone's initiative was inadequate and would not stem growing protectionist sentiment in the United States.

White House chief of staff Donald T. Regan, briefing reporters here while President Reagan vacations at his ranch, praised Nakasone's "unprecedented appeal" to the Japanese people to buy more foreign goods.

"The effort to open Japan's markets requires more than just the elimination of specific barriers," Regan said in a statement. "It requires a change in attitudes toward foreign imports.

"In this respect today's appeal is an important and welcome step," he said. "Changing deeply entrenched habits and attitudes is not an easy task."

Regan added that the recommendations of a Japanese trade commission include "few new or immediate market-opening measures," but said "an outline" of specific actions would be worked out by July.

He said "significant progress" has been made in talks on telecommunications, but "more remains to be accomplished."

In parallel talks on medical equipment and pharmaceuticals, forest products and electronics, as well as in telecommunications, "specific and concrete progress is needed urgently," Regan said.

That progress should result if the principles in Nakasone's address are followed, Regan's statement said.

While praising Nakasone's address urging Japanese to buy more American goods, Regan predicted that the Japanese actions would do little to reduce Japan's record $37 billion trade imbalance with the United States this year. The U.S. trade deficit "certainly won't get much better very quickly," he said.

Regan predicted that even with lower trade barriers and a weaker dollar, halving the trade deficit might take three or four years.

President Reagan, who has often expressed sympathy for Nakasone's political difficulties on the trade issue, was "pleasantly surprised" by the prime minister's appeal, Regan said. The president noted that Nakasone "didn't put all the blame" on the United States, he added.

Regan said a Senate resolution calling on Japan to open its markets to U.S. goods had "quite a jarring effect" on the Japanese. Those who pushed the resolution "accomplished the objective of getting Japan's attention."

The administration made virtually no effort to oppose nonbinding resolutions passed overwhelmingly in the House and Senate calling for retaliation against Japan if it fails to open its markets to U.S. goods. But the White House wants to head off actual bills enacting the retaliatory measures into law.

A senior administration official said at least one chamber is likely to pass such legislation, but the White House hopes it will not get to the president's desk, where a decision on whether to sign it would force Reagan to make a "no-win" choice between his free-market beliefs and rising pressure for protectionism in this country.

Vice President Bush said in a speech today that calls for retaliation in Congress could backfire on the United States.

"Whatever walls we dream of building, it's not walls we'd get if we started to live out a nightmare like that," he said in an address sponsored by the Export-Import Bank. "It's a cliff, and we'd find ourselves falling straight down to chaos."

Sen. John C. Danforth (R-Mo.), a leading backer of the Senate resolution, said Nakasone's television appeal was a "pack of promises" similar to unfulfilled Japanese promises in the past.

There was also criticism from the U.S. business community. "This looks like something that is long on promises but short on commitment," Jack McDonald, vice president of the Electronic Industries Association, told the Associated Press.

"We're looking for something much stronger in terms of commitments," he said. "This doesn't appear to be anything significantly new."

Larry Fox, vice president for international affairs of the National Association of Manufacturers, said Nakasone's effort was "totally inadequate."