The Reagan Administration is looking for a way to signal its approval of the new military regime in Guatemala and is considering lifting the ban on the sale of military hardware to that Central American country, administration officials said yesterday.

The administration is discussing a range of positive signals to Guatemala, including economic and political gestures and military sales, and may make a decision in the next 10 days, a State Department official said.

The Guatemalans are particularly anxious to buy spare parts for American-made helicopters used to counter a growing guerrilla insurgency in Central America's largest and most important country.

At the same time, the administration is considering additional punitive measures against Cuba, apparently to please conservatives at home while demonstrating a tough posture for possible future negotiations with the Cubans.

According to one senior official, the administration is considering a ban on sales to Cuba by foreign subsidiaries of U.S. corporations. Opposition by Latin American governments, particularly Argentina, undermined a similar ban that the United States tried to maintain in the 1960s and '70s.

In testimony to the House subcommittee on Latin American affairs yesterday, Assistant Secretary of State Thomas O. Enders praised the coup by junior military officers that has installed former Gen. Efrain Rios Montt as that country's president. Enders suggested that a firm U.S. policy toward the previous military regime helped make the coup possible.

"A promising evolution may have begun" in Guatemala, Enders said. "Since last month's coup led by junior officers, violence not directly connected to the leftist insurgency has been brought virtually to an end."

Earlier, Guatemala had been plagued by political murders and disappearances, many of which were blamed on government security forces.

"Concrete measures have been taken against corruption," Enders said. "All political forces have been called to join in national reconciliation. We hope that the new government of Guatemala will continue to make progress in these areas and that we in turn will be able to establish a closer, more collaborative relationship with this key country."

The administration is pursuing a complex diplomatic strategy in Central America, trying simultaneously to find carrots for regimes it deems friendly and acceptable and punishments for the two it considers particularly hostile, Cuba and Nicaragua.

Under sharp questioning, Enders refused to say whether the United States is involved in covert activities to destabilize the Sandinista regime in Nicaragua. The Washington Post has reported that President Reagan authorized a broad covert campaign against Nicaragua.

Rep. Gerry E. Studds (D-Mass.) read Enders the text of a 1970 U.N. Security Council resolution prohibiting all forms of armed interference by one country in the affairs of another and asked Enders if the United States still accepts the resolution.

"We regard it as one of the elements of international conduct to which we have reference," Enders replied.

Similarly, Enders refused to endorse specifically Article 18 of the charter of the Organization of American States, which also forbids members from interfering in any way in each other's internal affairs.

"Of course we support this OAS treaty," Enders replied. But he said only the House and Senate intelligence committees offer "appropriate" forums for testimony about possible covert operations.

After the subcommittee hearing, Enders confirmed to a reporter that the administration is considering further steps against Cuba. Earlier this week, the administration announced new moves intended to cut off U.S. business and tourist travel to Cuba.