The United States and the Soviet Union, in the newest arena of Cold War competition, are charging one another with violating the "Basic Principles of Relations" signed by the two superpowers as detente flowered in May 1972.

The current round of argument about the document, which has been all but ignored during most of the last decade, was prompted by the decision of Secretary of State Alexander M. Haig Jr. to make the code of conduct a basis for discussion with the Russians at the outset of the Reagan administration.

The State Department, following news reports that Haig has raised the issue with Soviet Ambassador Anatoliy Dobrynin, yesterday charged the Russians with undermining the effectiveness of the pact. Spokesman William Dyess pointed specifically to the Soviet intervention in Angola and Ethiopia and, most notably, the Soviet invasion of Afghanistan as violations of the agreed rules of superpower behavior.

The Russians, meantime, charged in a dispatch by Tass, the Soviet news agency, that a U.S. drive to achieve military superiority, as well as U.S. action to increase its military presence in the Persian Gulf and the Middle East, violated the agreement. Dyess denounced the Soviet charges as "clearly propagandistic in nature."

The document, signed by President Nixon and Soviet President Leonid Brezhnev in the Kremlin on May 29, 1972, sets outs 12 general principles of conduct, including "peaceful coexistence," "restraint" and a rejection of attempts by either side to gain "unilateral advantage."

The drive to obtain agreement on such a document originated with the Russians. The United States, at the time, approved a version of the pact as part of a package deal at a summit meeting notable for the fact it was held at all, on the heels of heavy American bombing and mining of North Vietnam, Moscow's ally.

Haig, who was involved in drafting the pact as a Nixon White House aide, is responsible for the revival of interest in the largely forgotten document, which is subject to a variety of interpretations by the two sides. State Department officials said Haig has not yet made it clear, however, whether he is insisting that the Russians agree to his interpretation of the 1972 pact and observe it, or whether he favors an attempt to negotiate a successor pact.

Haig has mentioned the U.S.-Soviet code of conduct in recent discussions with both Soviet and Italian diplomats, suggesting that Soviet observance of an agreed international code is a necessary condition of future agreements between the superpowers on a wide range of questions. President Reagan is reported to have brought up the matter in at least one White House meeting.

Dyess, in answer to questions, told reporters yesterday that "we intend to conduct our relations with the U.S.S.R. on the basis of reciprocity and restraint." He did not elaborate.