The Carter administration rejected yesterday the package of trade and economic proposals brought here by Japanese envoy Nobuhiko Ushiba, calling them inadequate to deal effectively with the huge Japanese trade surplus the United States wants to see pared back.

After a 4 1/2 hour meeting with Ushiba. Robert S. Strauss, the President's special trade negotiator, said that based on initial examination,the Japanese package was "insufficient, in our judgement" and "fell considerably short of what this country . . . feels is necessary."

Strauss told a press conference he had "expressed" the U.S. sentiments "very candidly to Mr. Ushiba, and I think he understood." He said she next step would be for the two sides to continue discussions and work toward "narrowing" their differences.

At the same time. U.S. officials cautioned that Strauss' reaction represented an initial assessment of the Japanese proposals, and did not imply any breakdown of the negotiations. Strauss said the talks were at such an early stage it was too soon to make any judgments.

The U.S. reaction appeared to underscore the determination of the Carter administration to remain firm in the talks with Japan. Earlier, more gentle efforts to persuade Japan to ease its trade restrictions produced no visible results.

Ushiba is scheduled to remain in Washington through Thursday to meet with other Cabinet officers and members of key congressional committees. The trade envoy told reporters last night he was satisfied the talks went well for the opening day.

There were hints that Ushiba may have brought some new proposals with him beyond those already announced in Tokyo. The earlier measures included a reshuffling of the Japanese cabinet, concessions on some tariffs and a proposal for a domestic economic stimulus program.

However, sources said any new initiatives were certain to be relatively minor, and were not easily identifiable in the administration's initial review of the Japanese package. Ushiba presented an eight-poing package yesterday, including tariff cuts on 300 items.

The Japanese envoy apparently made no effort to reply to an earlier U.S. demand - that Japan lay out a formal timetable for eliminating its burgeoning balance of payments surplus. The proposal had been the centerpiece of the previous U.S. recommendations.

However, there were indications yesterday that the United States has softened that demand to seek only "some progress" toward that goal, both in 1978 and 1979. The Japanese current account, or balance of payments, surplus is estimated at about $10 billion.

The meeting with Strauss was part of a round of conferences Ushiba had with top administration economic officials. The envoy met separately with Secretary of the Treasury W. Michael Blumenthal and Labor Secretary Ray Marshall. Vice President Mondale sat in with Strauss.

In his meeting with reporters, Strauss declined to spell out what the Japanese were proposing or what the United States was seeking. "Obviously, we have to bring about a substantial shift in their surplus," he said. "In the meantime, we've got have some short-range answers."

Strauss also sidestepped questions about whether he plans to go to Tokyo later this month to continue the talks with Prime Minister Takeo Fukuda, as had been suggested earlier. "I would guess that we will," he said, "but there's been no timetable set."

Ushiba's visits with other Cabinet members were described as more subdued. Sources say Marshall sought to explain the strong pressure from organized labor for new import quotas here, while Blumenthal discussed general economic policy.

American officials were reported to be unenthusiastic about Tokyo's tariffcutting proposals. Although Ushiba claimed the cuts would affect $1 billion in Japanese imports, administrations would be in areas of likely U.S. export.

The visit by Ushiba is in response to a U.S. move last month to begin pressing the Fukuda government for firm action to eliminate the burgeoning Japanese balance of trade and payments a surpluses - both by slowing its exports and allowing more imports.

Along with the reduction of the surpluses, the United States wants Japan to stimulate its ailing domestic economy, to reduce its subsidies to exporters and to lower quotas and tariffs on sales of U.S. and other foreign-made goods in Japan.

It was partly in reply to the U.S. prodding that Fukuda reshuffled his cabinet last month. One result of the shift was the creation of the new post held by Ushiba - minister for external economic affairs. Ushiba was ambassdor to the United States in the early 1970s.