FED UP WITH "political wranglings," the Pakistani army has ousted Prime Minister Zulfikar Ali Bhutto and promised elections and a return to civilian rule in 90 days. Regret at the spectacle of yet another military takeover must yield to recognition that Mr. Bhutto had run out his string. Coming to power after Bangladesh split off in 1971, this perversely brilliant figure did much to restore his nation's spirit and the momentum of its development. He held and won elections in 1973, but in new elections last March he rigged the results, without needing to, and the consequent protests and the army's eventual refusal to drag his chestnuts out of the fire brought him down.

To the extent that his troubles arose from personal hubris, rather than the economic and social conditions that tend to overwhelm the political leadership of most poor countries, there is a certain hope still for Pakistan. Or so the army seems to feel. The new man in charge, Gen. Mohammed Zia ul-Haw, insists he harbors no political ambitions. The lingering taste of the last term of military rule, culminating in the dismemberment of the country, is evidently still too strong for him to profess otherwise, Gen Zia faces formidable practical difficulties in settling the country down for new elections. Will he let Mr. Bhutto, still his party's chief, complete? At the moment, all the active politicians are in jail. Taking over is easier than letting go.

The United States has enjoyed generally good relations with Pakistan for decades, receiving Pakistan's cooperation in the name of global anti-communism, offering aid and a measure of protection against India. Even so, Mr. Bhutto at the end found it convenient to charge, without offering evidence, that the CIA was financing his opposition. Presumably the new leadership will have neither grounds nor political reason to foment anti-Americanism. It will then be quite feasible for the United States to continue cooperating with Pakistan on matters affecting the stability of its region as well as its own development. The Carter administration, at other times and places quick to identify failings of due process, passed off Gen. Zia's takeover as an "internal" matter. This leaves the way open, after a difficult interlude, for a return to mutually advantageous ways.