Washington — Spelling out the terms of the United States Navy's Lebanon mission in the clearest terms yet, Navy Secretary John F. Lehman Jr. says the Navy is providing supporting fire to the Lebanese army.
In a meeting with defense reporters, Mr. Lehman said, ''There is very definitely a shift in emphasis to make it clear that we will be providing supporting fire to the Lebanese armed forces. . . .''
cc20p6 Shortly afterward, White House spokesman Larry Speakes told reporters Lehman was in error, saying, ''Whatever we do . . . is in support of Americans and the multinational force.''
Also drawn into the controversy was the Pentagon, whose spokesman Michael Burch, said ''We're not providing fire in direct support of the Lebanese armed forces. . . . We're providing fire under the rules of engagement provided by the president.''
The Lehman statement followed a week marked by confusing statements from administration officials concerning the use of American naval gunfire in Lebanon.
First indications from the administration last week were that the gunfire was being used to protect the US marines in Beirut and the multinational force (MNF) of which they are a part. One case of naval shelling was in response to a rocket attack directed at the residence of the US ambassador in Beirut.
Finally, it became clear late last week that the Navy was supporting the Lebanese army even in cases where the marines were not endangered, but officials remained fuzzy on that issue. The administration's imprecision seemed to be caused by a desire to minimize charges from Lebanese and American critics that the US peacekeeping force was taking sides in a civil war.
Some congressional leaders, including House Speaker Thomas P. O'Neill Jr. (D) of Massachusetts, have charged that the policy of shelling Syrian and Druze artillery positions that were firing into Beirut was not within the purview of the Lebanon war powers resolution adopted by the Congress late last year.
President Reagan had declared on Feb. 7 that the new measures he had ordered in Lebanon, including the use of naval gunfire and air support, were consistent with the joint resolution worked out in October with the Congress concerning the MNF.
As recently as last Sunday, Secretary of Defense Caspar W. Weinberger reemphasized that the Navy was being used to protect the Marines and the MNF.
''The firing,'' Mr. Weinberger said, ''is not in support of any particular governmental unit or faction. The firing is . . . to try to silence fire that is endangering marines, multinational forces, (or) American interests in Beirut.''
In his comments, Navy Secretary Lehman went far beyond this, making it clear that the rules of engagement now include firing on forces that are attacking the US-trained and supported Lebanese army.
Questioned further on the issue, Lehman said that ''we are firing in response to firing into the Beirut area. It is no secret that the US government is supporting the Lebanese government. That's the whole purpose of our presence there.''
Some observers argue, however, that there is diplomatic advantage to be gained from maintaining at least an appearance of not taking sides in Lebanon. The fact the United States is so openly taking sides has disturbed American MNF allies and generated criticism from congressmen and Democratic presidential candidates.
But the main concern of the administration at the moment appears to be to emphasize it is not abandoning friends in the Middle East. In an interview with Knight-Ridder Newspapers on Monday, President Reagan said ''we haven't abandoned Lebanon.''
An administration official said in a briefing for reporters that when President Reagan met with Jordan's King Hussein on Monday the subject of the marines' pullback from Lebanon did not arise extensively. But the official said that the President made it clear that the planned Marine ''redeployment'' from Lebanon meant no change in US commitment in the region. Reagan was expected to deliver the same message in a Tuesday meeting with Egypt's President Hosni Mubarak.
Reagan, Hussein, and Mubarak have all emphasized in their meetings here this week that there is a need to pursue a broader Arab-Israeli peace process - aside from the need to resolve the Lebanon crisis - and to deal with the Palestinian issue in particular. But there was no indication that Reagan was ready to take steps in relation to the Israeli settlement on the West Bank of the Jordan River , which would apparently be required to bring Hussein directly into that broader negotiating process.
In his meeting with defense reporters, meanwhile, Secretary Lehman said that there was no evidence of any significant numbers of civilian casualties being caused by the battleship New Jersey in Lebanon. Muslim groups in Lebanon have charged that naval shelling has caused a large number of civilian deaths.
''First of all, when you are firing into an area, you can't guarantee that there won't be any civilian casualties,'' Lehman said. ''Those areas were supposed to be largely free of civilian habitation, but you cannot preclude hitting the odd shepherd in the hills, and you cannot preclude a short round or something like that. So area artillery fire is likely to produce some risk of civilian casualties but not nearly so much as the firing that it's meant to suppress and the civilian casualties that that fire produces in Beirut.''