Afghanistan and Pakistan will resume negotiations on a political settlement of the Afghan war in Geneva Monday amid reports the that Soviet Union will offer to withdraw its forces from Afghanistan in a year.

The Soviet offer, if forthcoming, could break the deadlock in the 5-year-old Geneva negotiations because a schedule for withdrawal of the 115,000 Soviet troops in Afghanistan has been the major stumbling block.

At the last session of talks in March, the Soviet Union, through the communist-backed Kabul government's delegation, offered to evacuate its forces within 18 months; Pakistan demanded that the withdrawal be completed within seven months. A Soviet offer of one year would appear to be an attempt at compromise.

The Kabul government suddenly sought another meeting of the U.N.-sponsored Geneva negotiations, and a Soviet source hinted here last week that Moscow is ready to withdraw in a year.

The negotiations are conducted under the auspices of the United Nations and involve only delegations from Afghanistan and Pakistan. They negotiate through U.N. mediator Diego Cordovez. Pakistan has refused to recognize the Soviet-backed Kabul government.

U.S. officials are reacting cautiously to reports of a change in the Soviet position. They said the administration has received no direct word from the Soviets about a withdrawal offer and that Deputy Foreign Minister Vladimir Petrovsky did not mention it in a meeting here Tuesday with Under Secretary of State Michael H. Armacost.

The State Department, however, announced Friday that it is sending Deputy Assistant Secretary of State Edward P. Djerejian to Geneva for talks on Afghanistan and the Persian Gulf. Djerejian will meet Thursday and Friday with Soviet Deputy Foreign Minister Yuri Alekseyev. The Soviets presumably could tell Djerejian of their withdrawal offer then.

A State Department official said the U.S.-Soviet meeting is part of an occasional exchange of views between the two governments on regional issues and is not linked to the Geneva talks between Pakistan and Afghanistan.

U.S. officials suggested that the reported new Soviet withdrawal offer, if it materializes, could be aimed more at persuading Pakistan to end its backing of the U.S.-armed Afghan resistance than anything else.

"The Soviets are trying to get the Pakistanis to decommit to the Afghan resistance," one administration source said.

Pakistan is the main conduit for U.S. military assistance to the Afghan guerrillas. A Pakistani acceptance of a one-year period before Soviet withdrawal could lead to a decision to shut the supply lines.

State Department spokeswoman Phyllis E. Oakley said Wednesday that the United States still wanted to see a Soviet withdrawal offer based strictly on logistical requirements to carry out such a process and completed "within months."

Another U.S. official said the United States would want to examine "the context" in which such a Soviet offer would be couched.

The official also suggested that the reported Soviet offer may be timed to the annual battle in the U.N. General Assembly over a resolution demanding that the Soviet Union withdraw its forces from Afghanistan. Last year, 122 nations supported the resolution. Several countries, including Zimbabwe and Iraq, may shift their vote this year, according to the official.

Administration officials have said that they do not believe the Soviet leadership has yet made "the hard decisions" necessary to withdraw its forces from Afghanistan in a year and abandon the weak Afghan communist government.

The Kabul government, at Soviet insistence, has been seeking to achieve a "national reconciliation" and form a coalition government that would include resistance leaders. It has recently offered to give the guerrillas posts in such a government and to allow formation of parties other than the communist one now in power.