U.S. and Soviet officials have drafted a declaration that provides a face-saving exit from Afghanistan and lets the Afghans decide how to settle the 12-year-old war, diplomatic sources said Monday.

The three-point declaration is deliberately vague and falls far short of bringing an end to one of the bloodiest and costliest conflicts of the 1980s, the sources said, speaking on condition of anonymity.It could be released this week during talks between Secretary of State James A. Baker III and Soviet Foreign Minister Eduard Shevardnadze in Houston, the sources said.

Washington's special envoy to the Afghan resistance, Peter Tomsen, was expected in Pakistan on Tuesday. He was prepared to explain any superpower announcement to the Afghan guerrillas who have been trying since 1978 to overthrow the Soviet-supported government in Kabul, the sources said.

"We anticipate an announcement. It's been in the cards for sometime. It may or may not happen this time. We're poised but it could be another false alarm," one diplomat said.

The announcement had been expected during last month's Baker-Shevardnadze talks in Geneva but was delayed by differences over how to cut off weapons to both warring sides, they said.

Moscow sent about 115,000 troops into Afghanistan in December 1979 to prop up successive communist governments trying to impose radical reforms on the largely rural Moslem population. After the Red Army's pullout in February 1989, Moscow continued to pour an estimated $2 billion to $3 billion annually in weapons and supplies to support troops loyal to President Najibullah.

Western diplomats and guerrilla leaders once confidently measured the survival of Najibullah's government in weeks and months. But the guerrillas were unable to switch from their hit-and-run tactics to conventional warfare and were rendered helpless against the well-equipped and well-trained Afghan air force.

Within months of the Soviet withdrawal, the anticipated guerrilla victory became a costly military stalemate that failed to produce a clear victory for either side.