The United States expressed its "grave concern" yesterday about Sudan's new military pact with neighboring Libya, which Washington considers a chief sponsor of international terrorism.

White House spokesman Larry Speakes said the administration had so far received only "sketchy" information about the agreement, which press reports said involved Libyan aid to Sudan for logistics, transport, air defense and training in the military field.

"We are conveying to the appropriate authorities in Khartoum our grave concern at the prospect of a military relationship between Sudan and Libya," Speakes said.

The United States has been the major arms supplier to Sudan for some time, providing $45 million annually the past two years.

Announcement of the Libyan-Sudanese military agreement appeared to have caught the administration by surprise. A State Department spokesman said the American Embassy in Khartoum had had no forewarning of Sudan's intention to sign such an accord with the regime of Col. Muammar Qaddafi.

The U.S. government had previously taken "extraordinary security precautions" to protect American diplomats stationed in Khartoum as a result of an influx of Libyans and what it regards as the "fluid situation" now prevailing there.

Since the April 6 coup that ousted President Jaafar Nimeri, a former close U.S. ally, the new Sudanese military leadership has been seeking to improve relations with Libya in a bid to persuade Qaddafi to cut off Libyan aid to an insurgency under way in southern Sudan.

State Department spokesman Robert Smalley said that Washington planned to warn the new Sudanese government that "a military relationship with Libya could only impact adversely on the ties between us."

"We have said that any improvement in Sudanese relations with Libya must not be at the expense of their ties with the United States," he said.

Another U.S. official said the accord appeared to be "a free-lancing agreement" worked out by the Sudanese defense minister, Maj. Gen. Osman Abdullah Mohammed, who had just spent more than a week in Libya meeting with Qaddafi and other top Libyan military officials.

Smalley said it was too early to say whether the military accord would have an adverse effect on U.S. aid to Sudan. But he said that he presumed the U.S. program to Sudan would be reviewed in light of the new accord with Libya.

Before the April coup, the United States had held up nearly $200 million in economic support funds to Sudan for fiscal 1984 and 1985 because of its arrears on payments to the International Monetary Fund and lack of a plan to improve the economic situation. The blocked 1984 portion was subsequently released, but the 1985 funds -- $114 million -- were not.