The pace of the Soviet troop withdrawal from Afghanistan and U.S. hopes for fair elections in Pakistan were topics for discussion Thursday between senior Reagan administration officials and Pakistani Foreign Minister Sahabzada Yaqub Khan.

There are an estimated 115,000 Soviet troops in Afghanistan. Half are supposed to be withdrawn by Aug. 15. Pakistani President Mohamnad Zia al-Haq raised concerns last week that the Soviets were replenishing them with new troops.Through Pakistan, the United States arms Afghan rebels fighting the Red Army and the pro-Soviet government in Kabul. The withdrawal is of major concern to Secretary of State George P. Shultz, Defense Secretary Frank C. Carlucci and the visiting foreign minister.

U.S. officials said this week that Moscow had sent new assurances that the Soviets would fulfill their commitment in the Geneva accords of last May to withdraw half the troops by Aug. 15.