The latest in a series of confrontations between Israeli forces and the US Marines in Lebanon dramatizes three issues of particular concern to Congress. These are: the War Powers Resolution, which is supposed to give lawmakers some control over the deployment of US forces abroad; aid to Israel; and just how long the Marines will have to stay in what is becoming an increasingly difficult and dangerous situation.
A Senate Foreign Relations Committee source says Congress is unlikely to take specific action unless a loss of American life occurs. Some lawmakers, in their frustration, are questioning American aid to Israel. But any changes here seem highly unlikely, according to administration and congressional sources.
Under the War Powers Resolution, adopted in 1973, the President needs congressional approval to station US troops overseas for more than 90 days if it is determined that they are being sent ''into hostilities or into situations where imminent involvement in hostilities is clearly indicated by the circumstances.''
So far, the administration has contended that the US marines are not in a hostile environment, and that there is therefore no time limit on their stay. Some lawmakers, including Sen. John Glenn (D) of Ohio, note that one marine already has been killed in Lebanon (by an unexploded Israeli cluster bomb left over from the war there), and that this constitutes hostilities.
Sen. Thomas F. Eagleton (D) of Missouri, who took part in drafting the War Powers Resolution, argues that President Reagan ''is violating the spirit if not the letter of the law.''
Law Prof. Michael Glennon of the University of Cincinnati, former legal counsel of the Senate Foreign Relations Committee, notes that key words in the resolution - ''introduced'' and ''hostilities'' - are undefined.
Writing in this newspaper recently, he noted: ''There is little question that its failure to define critical terms and to require specificity in reports has left the door open to semantic circumvention.''
The assignment of 1,200 Americans as part of the 4,300-man multinational force in Lebanon is the kind of job the Pentagon likes least - being interposed as a highly exposed but heavily constrained buffer between warring parties while diplomatic efforts drag on.
Secretary of Defense Caspar W. Weinberger and senior uniformed officers have made no secret of their uneasiness over the escalating series of incidents between Israel and the US, and of their desire to have the marines leave Lebanon as soon as possible.
Several months ago, the administration was predicting that the marines would be able to return to the United States by the end of 1982. But Assistant Secretary of State Nicholas Veliotes told a congressional committee this week that US forces may have to remain through 1983.
The incident involving three Israeli tanks and a Marine captain was the sixth in a series that began in January.
It illustrates three things: a difference of opinion between the US and Israel over the role of the multinational force; continued uncertainty over which forces control what territory around Beirut; and Israel's increasing frustration over continued attacks on its troops. Such attacks have left 30 Israeli soldiers dead and 183 injured since the war in Lebanon supposedly ended five months ago.
By Thursday, the rhetoric over this week's confrontation had subsided somewhat, a US spokesman calling it an ''apparent misunderstanding'' over lines of control. Israeli and US commanders on the scene was reported to have worked a new agreement on the demarcation line dividing their jurisdictions.
But this leaves a basic problem unresolved: Israel believes its troops continue to be attacked by Palestinian forces coming from within areas assigned to multinational force units.
In Washington, there is thus the growing realization that, not only might the marines be in Lebanon for an extended period, but that they could be exposed to increasing risks if the attempt to remove foreign forces from Lebanon does not succeed.