It was good to hear President Reagan and later Defense Secretary Weinberger play down any likelihood of US military participation in the latest flare of tension between Egypt and Libya. Despite the Arab neighbors' efforts at fence-mending last year, Egypt's President Mubarak is reported to be freshly concerned about Libyan leader Qaddafi's intentions toward another neighbor, Sudan. A Libyan military buildup along the border with Sudan was cited by US defense officials in noting dispatch of four AWACS surveillance planes to Egypt and temporary movement of the aircraft carrier Nimitz from Lebanese waters to the vicinity of Libya.
In his Wednesday news conference Mr. Reagan said that the US was not doing anything unusual in the area. He said he knew that Sudan was one of the states that Colonel Qaddafi has threatened. But he said use of American forces to stop Qaddafi has never been contemplated. This was in keeping with Mr. Reagan's welcome pledge during another time of tension that US troops would never be used in Sudan. That was in 1981 when he was seeking to expedite military aid to Sudan against possible encroachments by Libya through Chad.
Now, as then, Sudan's internal political and economic problems are more of a realistic threat to long-term stability than Libyan arms. The easing of these problems could foster conditions resistant to Libyan destabilizing efforts.
Even the unpredictable Qaddafi, for all the antagonism between him and Sudan's President Nimeiry, may not be so reckless as to risk an all-out invasion. There are a difficult 600 miles of almost roadless desert between the Libyan-Chad border and Sudan's capital of Khartoum.
The point is that Qaddafi is unpredictable, as his previous adventurings in Chad have shown. Indeed, it is a pity that one who has done so much for domestic progress in Libya, should have built himself an international notoriety for dangerously erratic belligerence.
Thus, when Egypt calls for help in the air watch over Libya, the United States cannot take the request lightly. At the same time, the US must act in accord with what Secretary Weinberger affirmed the day after the presidential news conference: ''We only go where we're asked, and we don't get into any kind of military activity without adherence to the War Powers Act.''