State Department officials are awaiting the return to Washington this week of special Middle East envoy Philip C. Habib so that work can begin on a specific proposal for getting Israeli, Syrian and Palestinian forces out of Lebanon as fast as possible.

President Reagan, administration officials say, asked the State Department late last week to accelerate such planning and come up with a specific formula and a timetable for the hostile forces' withdrawal.

Aides say the president is concerned that the best moment for pressing all sides into a withdrawal may be now and that this will become increasingly difficult.

They add that Reagan has not put forward any timetable of his own but rather is seeking to push the bureaucracy to come up with a plan that contains concrete steps.

At the moment, one official said, "there isn't a plan that meets the expectations, has a timetable, and is specific and goal-oriented enough for the president."

Soon after the president made it known that he wanted more concrete planning from the State Department, an Israeli bus was ambushed Sunday in Lebanon, killing six soldiers; yesterday Israeli warplanes attacked Syrian and Palestinian positions in northern and eastern Lebanon.

That kind of attack and apparent retaliation will continue and make a settlement impossible unless both sides begin to withdraw very soon, officials said.

Aside from a mission to help the Lebanese government reassert control over its own country, the question of withdrawal of Israeli, Syrian and Palestinian forces is also a factor in how long peace-keeping American Marines and French and Italian troops stay in Lebanon.

Reagan and other American officials have spoken publicly of the Marine deployment as being "of limited duration," a matter of weeks rather than many months, it is hoped. The Pentagon, in particular, is anxious to get the warring parties out of Lebanon so the Marines' stay will not be extended.

Reacting to Washington Post report yesterday that the Marines, according to government officials, could be in Lebanon for a minimum of four months, Defense Secretary Caspar W. Weinberger is understood to have told associates that there is absolutely no thought now of keeping the troops there that long, barring some unexpected development.

The State Department's response to the White House call for a more detailed plan is centered around the return of Habib, who has just completed a tour of five Middle Eastern nations. Habib is expected to meet with top State Department officials and then with the president.