Nicaragua formally charged today that the U.S. National Security Council is guiding strategy and choosing the military targets of the counterrevolutionary guerrillas fighting to overthrow the Sandinista government.

Carlos Arguello, Nicaragua's chief counsel and ambassador to the Netherlands, contended that this year the administration has assumed an ever greater role in orchestrating attacks by the rebel forces, known as contras, or counterrevolutionaries.

Arguello, speaking before the International Court of Justice at the start of hearings against the United States for alleged involvement in military actions against the Sandinistas, said his country would produce witnesses and documents "to prove beyond a doubt that the U.S. government has set justice aside and is guilty of state terrorism."

The United States announced in January a boycott of the proceedings after the court, known informally as the World Court, ruled last November that it held jurisdiction and would hear the merits of the case. Washington had argued in vain that Nicaragua never previously recognized the court's authority and was now seeking to exploit the forum for propaganda purposes.

Saying, "the seat of justice is definitely empty in the United States," Arguello told the court's 14 judges: "Your authority is being challenged by a superpower that wishes to set law aside in order to have a free hand for destroying a small nation."

Despite the absence of U.S. legal representatives, Nicaragua will not be awarded the case by default and must persuade the court of the validity of its claims. If the court decides in its favor, Nicaragua will then seek financial compensation for the damage inflicted by anti-Sandinista forces.

Arguello charged that White House involvement in the contras' military actions has become so evident lately that, "in effect, the commander in chief of the U.S. armed forces is also the commander in chief of the contra forces."

Arguello introduced a sworn affidavit from Edgar Chamorro, a former leader of the Nicaragua Democratic Force, the largest contra group. Chamorro's statement described detailed meetings with members of the Central Intelligence Agency and the National Security Council.

He recalled an encounter in May 1984 with Ronald F. Lehman, an NSC aide, who assured him that after the 1984 election President Reagan "would publicly endorse our effort to remove the Sandinistas from power and see to it that we received all the support that was necessary for that purpose."

Nicaragua's legal team plans to emphasize the more active involvement by the U.S. government in exerting military pressure on the Sandinistas despite an earlier court order to desist from the threats or use of force, according to Abram Chayes, a Harvard law professor and former State Department legal adviser who is serving as counsel for the Sandinista government.

The first witness brought by Nicaragua today was Commander Luis Carrion, the country's deputy interior minister, who is also the Sandinista commander in charge of the military region where most of the fighting has occurred.

Carrion said that since the United States began organizing contra attacks in December 1981, the rebels have doubled in strength to 7,000 soldiers equipped, trained and paid largely by the U.S. government. President Reagan said in February that there were 15,000 rebels fighting the Sandinistas.

In the past two years, Carrion said, American or Latin American agents hired by the CIA had participated in several attacks, including the sabotage of an oil storage depot at the Pacific port of Corinto that required the evacuation of 20,000 persons. He accused CIA agents also of blowing up a major oil pipeline and staging air attacks with combat planes and helicopters.

In an assessment of the human cost, Carrion said 3,886 persons have been killed and 4,731 wounded in contra attacks since they began nearly four years ago. Property damage, he said, is estimated to be $375 million