The Reagan administration is considering when to lift economic sanctions imposed against Argentina after the Argentine invasion of the Falkland Islands, according to administration officials.

Although no final decision has been made, some administration officials say they expect the sanctions to be lifted "in the near future," as one official put it.

While the U.S. sanctions imposed April 30 were largely symbolic, officials say their removal now would signal the junta in Buenos Aires and other Latin American countries that the United States wants to begin patching up hemispheric relations damaged by the British-Argentine war.

At the same time, officials say, they would signal London that U.S. backing for the British position during the fighting is not entirely open-ended now that London's military objectives have been achieved.

British Prime Minister Margaret Thatcher, who arrived in New York to address the United Nations session on disarmament this morning, is to meet with President Reagan at the White House late this afternoon.

Officials say they cannot be sure what the president will say to Thatcher privately. But administration sources say Reagan's advisers have been recommending that he "try and temper her euphoria" over British military success, determine her long-term plans and make clear that a protracted British military solution in the Falklands creates problems for U.S. hemispheric interests.

White House officials say they expect Reagan to express admiration for the British military operation and for Thatcher's leadership, and to reiterate U.S. support for countering aggression.

But they expect him to suggest that U.N. Security Council resolution 502, which was adopted April 3, a day after Argentina's invasion, and which calls for a diplomatic solution to the crisis, be the basis for a long-term settlement.

While officials do not expect Thatcher to embrace the White House view, they feel that it is important that she hear it from Reagan.

Just as the United States expects to lift its sanctions as a step toward maintaining relations with moderate influences in Argentina, U.S. officials believe that the British must work out some kind of a settlement that Argentina's totalitarian regime can live with.

Despite the British military victory, some U.S. specialists believe that the situation in the South Atlantic remains dangerous. They note a continually humiliated Argentine leadership may conclude not that aggression does not pay but rather that Argentine forces simply lacked enough of the proper type of weapons.

Some specialists believe that, with a small turn of events, the Falklands battle could have become a disaster for Britain.

For example, a French-built Exocet missile, apparently aimed at a British aircraft carrier laden with jet planes and a large crew, hit and sunk a nearby cargo ship. Had the carrier been hit, some officials speculate, the military picture might have changed.

Thatcher, having taken large political risks in dispatching the British task force, also has taken a hard-line stance on the future of the Falklands, essentially turning aside not only the earlier advice of the Reagan administration but also of her own Foreign Office.

She has ruled out giving Argentina any say in the islands' future and apparently intends to turn them into a permanently defended bastion.