The Reagan administration, charging that the International Court of Justice is being misused "for political and propaganda purposes," said yesterday it will boycott further court proceedings on U.S. support for guerrillas trying to overthrow the government of Nicaragua.

The walkout comes two months after the court rejected administration arguments that it lacked jurisdiction in the case, which was brought by the Nicaraguan government.

At the same time, U.S. officials said that the administration is halting talks between special ambassador Harry W. Shlaudeman and Nicaraguan Deputy Foreign Minister Victor Tinoco until the United States makes a new assessment of whether the leftist regime in Nicaragua is cooperating in the Contadora discussions of possible regional solutions to Central American conflicts.

Administration officials said the boycott applied only to the Nicaraguan case, and that the United States has no intention of ending its support of the World Court. However, State Department spokesman Alan Romberg said:

"We profoundly hope the court does not go the way of other international organizations that have become politicized against the interests of the Western democracies. Such a development would do grievous harm, both to the court as an institution and to the rule of law."

The two actions appeared to signal a heightening of the administration's tough line toward Nicaragua -- a nation the United States charges with supporting leftist guerrillas in El Salvador and acting as a base for communist subversion in Central America.

Critics of the administration's Central American policy reacted strongly to the announcement. "I am shocked and saddened that the Reagan administration has so little confidence in its own policies that it chooses not even to defend them," said Rep. Michael D. Barnes (D-Md.), chairman of the House subcommittee on Western Hemisphere affairs.

Sen. Claiborne Pell (D-R.I), ranking minority member of the Senate Foreign Relations Committee, added: "The decision compounds the damage already done by the involvement of the United States in the mining of Nicaraguan harbors and the funding of contra forces . . . . "

The officials also denied Nicaraguan charges that the United States is pulling out of the Shlaudeman-Tinoco talks, the special communication channel agreed upon when Secretary of State George P. Shultz visited Nicaragua last year. But, while insisting that the administration wants to continue talking, they made clear that resumption would be linked to U.S. assessment of how cooperative Nicaragua appears to be in the next Contadora talks in February.

Senior State Department officials, speaking with reporters on condition they not be identified, said the decision to have U.S. representatives walk out of the court proceedings in the Hague was based on the administration's contention that the court was "clearly erroneous" in declaring that it could take jurisdiction over Nicaragua's suit.

Nicaragua brought its suit in the U.N.-affiliated court last April after revelations that the CIA had assisted Nicaraguan rebels, called contras, in mining Nicaraguan harbors. In an interim judgment last May, the court urged the United States to halt all activities that jeopardize Nicaragua's "sovereignty and independence."

Then, in November, the 16-judge panel rejected, 15 to 1, the U.S. argument that it lacked jurisdiction and decided to accept Nicaragua's suit, opening the way for hearings on the merits of the Nicaraguan charges and its demand for compensation. The dissenter was an American judge, Stephen Schwebel.

Administration sources said the decision to refuse to cooperate further was made after intensive discussion in recent days with government lawyers and outside experts on international law. According to sources, there was agreement among most of the lawyers consulted that the United States could make a good legal case for refusing to accept the court's authority on the grounds that most other countries have put strict limits on their willingness to accept its compulsory jurisdiction.

However, the sources acknowledged, the administration encountered sharp divisions within the legal community about the wisdom of acting solely on that legal point. The sources said that many of the experts consulted argued that the United States should permit the case to go ahead and be argued on its merits as a means of underscoring U.S. respect for international law and preventing world opinion from getting the impression that the United States has something to hide.

Sources said the administration decided it could not proceed because further hearings would expose the degree to which the United States has aided the contras and make clear that it also has failed to observe provisions of the U.N. Charter and the Inter-American Treaty on Hemispheric Defense in its activities against Nicaragua. That, they said, would give Nicaragua a major propaganda victory and subject U.S. intelligence activities to potentially serious damage.

A lengthy statement issued by the State Department sought to deflect the impression that the United States is afraid to let the merits of the case be aired in an international forum. It said:

"Nicaragua's efforts to portray the conflict in Central America as a bilateral issue between itself and the United States cannot hide the obvious fact that the scope of the problem is far greater . . . .It is clear that any effort to halt the fighting would be fruitless unless it were part of a comprehensive approach to political settlement, regional security, economic reform and development, and the spread of democracy and human rights.

"The conflict in Central America, therefore, is not a narrow legal dispute; it is an inherently political problem that is not appropriate for judicial resolution. The conflict will be solved only by political and diplomatic means -- not through a judicial tribunal."

In discussing the decision about Shlaudeman, U.S. officials privately acknowledged that he originally had agreed to meet with Tinoco during this month. But, they added, the United States changed its mind because of a feeling that Nicaragua was trying to divert issues that Washington wants discussed in the Contadora process to the bilateral talks.

"We wanted to close off that escape hatch," one official said. "Our intention is to make a decision about when and if to resume the talks after we see what happens in the next Contadora round in February."