Libyan leader Muammar Qaddafi, speaking by satellite to a Black Muslim convention here, urged black soldiers in the U.S. military to desert and join black American civilians to fight against "your racist oppressors" and establish a separate nation.

"This imperialist country must be destroyed," Qaddafi said. "Otherwise the nation of blacks will be destroyed, Islam will be destroyed, the state of Red Indians will be destroyed. We are ready to give you arms because your cause is just. We are with you, don't worry. You have to trust us . . . . The final victory will be soon."

Qaddafi was introduced to the more than 15,000 here by Nation of Islam leader Minister Louis Farrakhan as a "fellow struggler in the cause of liberation of our people." Farrakhan said Qaddafi is a "backer of revolutionary struggle throughout the world, something the United States should be part of . . . but instead brother Qaddafi is singled out as being a living monster."

Farrakhan, however, later also praised President Reagan, saying that God had sent him to force blacks to become self-sufficient through cuts in the budget for social programs.

Farrakhan, a black separatist, did not comment on Qaddafi's remarks, but concentrated on an economic rebirth in the black community.

"The problem is the black leadership is looking to Washington to provide us the program [to help blacks]," Farrakhan said. "No, no, no. Thank God for Ronald Reagan . . . [God] gave you Reagan to cut back, cut back . . . . Now you've got to look to yourself and organize so together we will lift ourselves from this condition."

Qaddafi, appearing on a large-screen television, told the Muslims and blacks gathered in an armory here in a poor section of Chicago that "America is not a land of whites only." He said blacks and American Indians -- several hundred of whom are attending this convention -- are "victims of racism and the destruction by whites in their continent."

Qaddafi said U.S. whites have refused to grant blacks and Indians either political or social power and the only recourse is for the minority groups to secede from white America.

"They refuse to see you as citizens in America," Qaddafi said. "What does this mean? We are to create a separate and independent state, a sovereign state in America . . . .

"It is very shameful to see a superpower and great nation like America committing this sin against you. You have the right to struggle, to create a sovereign independent state."

Qaddafi said the army necessary for blacks to form their own nation is to be found in the 400,000 blacks in the U.S. military. He said "that great number" of blacks in the armed forces means that whites are using blacks to die in wars fought for purposes determined by whites.

"We call then for you now to leave the Army -- the Army of America -- and come back to your brothers, blacks. This number is enough to create a strong army for you, to protect you and to defeat your enemy."

At one point in his half-hour speech, Qaddafi, pointing to his hair, said that in the United States he would be considered black by whites "because my hair is curly like yours."

"It means we are all blacks in the struggle," he said, "in freedom, in Islam. We are black to our brothers' enemy."

Qaddafi noted that the income of black American families is about half of the income of white American families and suggested that is justification for a revolution because "the wealth of America is for all, black, red and white . . . . This is unjust and so we have to struggle . . . . "

"Why does Reagan have the right to be president of America and blacks and Indians not have the right to be so?" said Qaddafi. "You have to struggle if they don't want you to be American citizens.