Secretary of State Alexander M. Haig Jr., in conversations with both Soviet and Italian officials, has made clear that the United States wants Moscow to observe an agreed code of international conduct as a condition of future negotiations on a broad range of East-West issues, informed sources said yesterday.

Haig told visiting Italian Foreign Minister Emilio Colombo yesterday that Moscow should go back to observance of a code of conduct similar to that adopted by the two superpowers in May 1972, calling for reciprocity and mutual restraint in international affairs, according to diplomatic sources.

Haig and the Italian official agreed that Soviet actions in Afghanistan, Africa and elsewhere had disturbed the global equilibrium. The sources quoted Haig as saying that steps toward restoration of this balance and a demonstration of Soviet restraint are essential conditions for future negotiations.

Similar statements reportedly were made by Haig in a confidential meeting last week with Soviet Ambassador Anatoliy Dobrynin. According to one account, that of ABC News correspondent John Scali, Haig said then that "all new Soviet-American agreements, including arms control, trade and financial credits, will be held up" until there is new understanding on the limits of Moscow's activities throughout the world.

U.S. sources confirmed that such a conversation took place, possibly at an intimate dinner Feb. 5 at the home of Sen. Charles H. Percy (R-Ill.), chairman of the Senate Foreign Relations Committee, with only Percy, Dobrynin and Haig in attendance.

Moreover, both U.S. and Soviet officials suggested that the authoritative report by Scali Tuesday night on the confidential Haig-Dobrynin meeting may have played a role in the unusual Soviet action Wednesday to make public the text of Soviet Foreign Minister Andrei A. Gromyko's first substantive communication to the Reagan administration.

The State Department yesterday expressed regret at what spokesman William Dyess called the "virtually unprecedented" release by the Russians of a confidential communication with the United States. However, State refused to release Haig's part of the exchange of letters with Gromyko on grounds that "preservation of confidentiality" is very important.

Haig, then Henry A. Kissinger's senior aide as deputy national security adviser to President Nixon, had a hand in the drafting of the Basic Principles of U.S.-Soviet Relations" signed by Nixon and Soviet President Leonid Brezhnev in Moscow on May 29, 1972.

At the time, the Soviets placed much more importance on the broad generalities of the document than did U.S. officials. But as the years have gone by, Haig and some other American strategists have charged the Soviets with violating the code of conduct by acting without restraint to seek unilateral advantage abroad.

Haig and his new leader, Ronald Reagan, have firmly linked Soviet activities throughout the world with future agreements on arms control and other issues. The recent remarks by the new secretary of state suggest that the demand of adherence to an agreed code of conduct, either the 1972 principles or a successor pact, will be the Reagan administration's diplomatic expression of its insistence on Soviet restraint.

The Soviet Union in the past has contested the U.S. interpretation of the requirements of the "basic principles," saying that Moscow never gave up the right to assist "liberation forces" in the world and charging the United States with violations of the code. There is no indication the Russians are prepared to agree to the U.s. interpretation now, especially in the embittered climate of Soviet-American relations that marked the early weeks of the Reagan administration.

In his meeting with Haig, the Italian minister stressed the importance that the west European allies attach to the long-stalled strategic arms limitation talks between Moscow and Washington. The Italians expressed hope that those talks will proceed, though they agreed that some restoration of Soviet restraint must be taken into account.

Haig did not say precisely under what conditions the United States would go back to the SALT negotiating process, according to the sources, but the Italians drew the conclusion from the talks that there could be no major negotiations linked to detente until there was some restoration of restrained behavior of Moscow.

Colombo is the first of several ministers from key European allies scheduled to visit Washington in coming weeks. His visit, however, was especially important since he will meet in Brussels Monday with the nine other foreign ministers of the European Economic Community and deliver the initial firsthand account of Reagan administration thinking.

Colombo is said to have told Haig that Italy was opposed to any more restricted western summit meetings such as the one held in Guadeloupe a few years back ago that included the United States, France, England, Britain and West Germany but left out other allies. Haig reportedly assured the Italians that won't happen again.

The Italians also confirmed their intention to stick to the agreement reached in NATO in Decmeber 1979 in which new U.S. missiles will be based in Italy, West Germany and Briain. That decision by the Italian government was crucial to acceptance of the NATO armament plan and several U.S. officials have pointed out since then that Italy was playing a larger and more positive role in the western alliance than has been commonly realized here.

In addition to Haig, Colombo also met with President Reagan and Vice President Bush. Italian officials said the meeting with the president went extremely well.