Egyptian President Anwar Sadat today sent his top aide to Washington with a "very urgent message" for President Reagan on what appears to be a growing likelihood of military confrontation between American-backed Sudan and Soviet-supported Libya along the Sudanese border with Chad.

Egyptian Defense Minister Lt. Gen. Mohammed Abdul Halim Abu Ghazala told reporters that the special envoy, Vice President Hosni Mubarak, was going to ask Washington to send additional arms, including antiaircraft missiles, to Sudan.

Tuesday, Sudan charged that Libyan Migs had been bombing Sudanese villages along the border with Chad for the past 19 days and threatened retaliation if they did not stop.

Libya has more than 10,000 troops stationed in Chad to bolster the shaky government of President Goukkouni Oueddei in its battle with guerrilla forces led by Hissan Habre, who is backed by Sudan. In the past two months, there has been an upsurge in fighting between the two sides.

Egypt, which is linked to the Sudan in a defense alliance, has been showing mounting concern about the conflict as well as the intentions of Libyan leader Muammar Qaddafi toward Sudan. Qaddafi, the sworn enemy of Sudanese President Jaafar Nimeri, has been involved in several attempts to oust him.

"We think the Soviets and the Libyans are going to do something through the borders with Chad in order to divert attention from something that is maybe going to happen in Poland," Ghazala told reporters.

He described the situation as "more dangerous" for Nimeri than in 1976 when more than 1,000 Sudanese dissidents trained in Libya infiltrated Sudan and nearly succeeded in ousting him.