Opposition from leaders of Japan's ruling Liberal Democratic Party forced the Japanese government today to postpone tariff cuts demanded by the United States on tobacco and by the Common Market on chocolates and cookies as part of a package of tariff cuts on 75 imported products.

The list of items is being sent to the official tariffs council for its virtually automatic endorsement.

Political sources said the rift between the cabinet and party leaders underlined the difficulty the government faced in easing imports of U.S. and community goods which could threaten the livelihood of major Liberal Democratic Party backers such as farmers.

"Party members demanded the postponement because the government's hasty decision would cause a lot of problems within the party in persuading members concerned," one party official said.

Liberal Democratic sources said that party members, taking a tough stand to appease their farming constituents, eventually will go along with the government's decision, but could not say when such a consensus would be reached.

The government has been trying to push through new tariff cuts, in addition to a major market-opening package announced last May, for implementation next April, ahead of Prime Minister Yasuhiro Nakasone's visit to the United States next month.

The government had planned to cut the tobacco import tariff to 20 percent from 35 percent, and the cookies and chocolates tariff to between 20 and 24 percent from between 32 and 36 percent.

Today's cuts cover 28 manufactured items ranging from tractors to handkerchiefs and 44 agricultural items including such minor products as papayas and mixed vegetable juices.

Imports of manufactured goods affected by the cuts announced in May and today were valued at $3.3 billion in 1981, or about 2 1/2 percent of total imports.

The United States ran an $18 billion trade deficit with Japan last year and has pressed Japan to accept more goods or face retaliation from Congress.

Approval by the council, an advisory body to the prime minister, was expected to be automatic. Foreign Minister Shintaro Abe even scheduled a meeting with U.S. Ambassador Mike Mansfield later in the day to inform him of the new measures, foreign ministry sources said.

But the meeting was called off as opposition from the powerful LDP farm caucus forced the government to hold back on making the tariff-cutting program official, the sources said.

A government source called the about-face an "unprecedented move."

An official in the Agriculture, Forestry and Fisheries Ministry said he expects the controversy over tobacco, chocolate and biscuits to be settled by the end of the year.

He said that one problem was the absence of provisions in the plan to reduce the domestic Sugar Consumption Tax. The current tax would make it impossible for domestic producers to compete with imported products if tariffs on chocolate and biscuits are cut, he said.

Once approved by the LDP-controlled parliament, the new tariff cuts would go into effect on April 1, together with cuts on 240 other items announced on May 28.

Beef and oranges, which along with tobacco have been the subject of intense lobbying by U.S. trade officials, were not included in the list of trade concessions announced today. Chocolate and biscuits were among items in the May package, but European Economic Community officials have pushed for further reductions.

On Thursday, the United States had reassured Japan that, for the time being, it will not file a complaint with the General Agreement on Tariffs and Trade on 17 items for which Japan has residual import restrictions.