Ugandan President Idi Amin announced yesterday that he is unconditionally withdrawing troop sfrom Tanzania, but Tanzania immediately denounced the statement as a "complete [WORD ILLEGIBLE] ".

Amin's move was announced in cases to the Organization of African Unity, the United Nations and the Arab League and was broadcast on Radio Uganda.

Two weeks ago, Amin's troops invaded a 710-square-mile section of northern Tanzania and declared it annexed. Well-informed sources said there was no evidence yet of a Ugandan withdrawal but said it is clear that Amin is under considerable pressure to end the border war.

The Tanzanian government gives little credence to the often contradictory statements of the erratic Ugandan dictator. In a statement it said: "The truth of the matter is that Amin is not withdrawing his troops. By his own admission, and that of his various spokesmen, he is reinforcing his aggressor troops."

On Monday Amin had announced that he was going to the warfront to personally lead his troops into battle.

Even if Amin withdraws his forces, Tanzania officials appear far from willing to simply let the matter pass. In the Tanzania view, the conflict is no longer over who controls the land north of the Kanera River. The Tanzanians appear determined to punish Amin for the killing, raping and pillaging allegedly done by his soldiers in Tanzania.

"Would you then say to the gang that everything is okay because they are no longer in the house?" one high official asked, likening the Ugandans to a gang of bandits. "We are very angry and we don't believe Amin should get away with this."

Tanzanian troops have been engaged in a massive counteroffensive against Uganda. Foreign Ministry officials here have been telling diplomats that Tanzanian forces have "hit the Ugandans hard" since their counterattack began Saturday night. No orders were issued to Tanzanian troops to slacken their drive after the Ugandan announcement, government sources said.

The United States, Britain several other Western countries and numerous African states have all come out strongly on the side of Tanzania. Knowledgeable sources say that Kenya, which is Uganda's lifeline to the sea, may be holding up shipments of vital supplies, particularly oil, to Uganda.

Since the United States imposed a trade embargo on Uganda last month, no major oil company has taken up the 45 percent of Uganda's soil formerly supplies by American companies. A Tanzanian government delegation visited Kenya last week, apparently to discuss imposing a blockade against Uganda.

Special correspondent Victoria Britain reported from Nairobi, Kenya:

Diplomatic analysts said Amin must have concluded that he had sufficiently suppressed the army mutiny that apprently led to his troops' border crossing two weeks ago. Otherwise, they suggested, the Ugandan dictator would not have risked retreating from a military adventure boost in years because it had humiliated the Tanzanians.

Following his occupation of th Kagera salient, Amin was reportedly able for the first time in years to walk the streets as a hero by the people who have lost virtually their whole intellectual and middle classes in his purges.

Intense pressure from Arab and African diplomatic circles apparently has been one important factor in Amin's apparent policy shift. Envoys from the organization of African Unity have flown back and forth between Kampala, the Ugandan capital, and Dar es Salaam for the last tow weeks and Uganda has been urged to settle its differences with its neighbor by such a disparate group of countries as Saudi Arabia, Libya, Iraq, the Soviet Union, Kenya and Guinea.