Young Jordanians by the hundreds filed into armed forces offices today to join the volunteer force that Jordan's King Hussein is sending to fight alongside Iraq in the war against Iran.

At one Army conscription office turned into a volunteers' acceptance office, about 100 young Jordanians were busy being processed to join the "Yarmouk forces" volunteer unit whose formation King Hussein announced Thursday night.

Iranian Deputy Foreign Minister Ahmed Azizi was quoted by Tehran radio as saying, "Hussein's call for the formation of a volunteer force is regarded by Iran as a declaration of war," but there was no indication how Iran would respond, United Press International reported from Beirut.

Most of the volunteers at the Abdali office in central Amman said in interviews that they were joining the Yarmouk forces because of their desire to contribute in a practical manner to the defense of what they called "Arabism and the Arab nation." Another common theme was the willingness to get battlefront experience in the Iraqi-Iranian war as preparation for what they called "the number one enemy of the Arab world, Israel."

Many of the volunteers are youths who recently have completed their obligatory service in the Jordanian armed forces, and therefore could be sent to the front with only slight retraining.

The volunteers did not know exactly when they would travel to Iraq but said they assumed that they would go in with the first contingent of the Yarmouk forces within several weeks. That contingent is expected to be led by King Hussein, who said he would go to Iraq to spend as much time as possible with the volunteer force.

There have been no government announcements on any aspect of the volunteer force today. Armed forces officials who usually comment on such matters said an announcement on more details of the Yarmouk forces would be made soon.

King Hussein's call for all Arabs to come to the aid of Iraq has elicited some support in the Persian Gulf oil states, but has also drawn the anger of Syrian and Libyan officials. The Jordanian move is likely to become increasingly controversial both in the Arab world and abroad.

At a briefing Friday, a U.S. spokesman said the State Department would "have to wait and see what develops" before specific comment on Jordan's move, which it said appeared to involve volunteers and not regular Jordanian Army units.

"As we have said since the outbreak of fighting, we do not want to see the conflict widen," the spokesman said. "Our concern over any action that would tend to widen or prolong the war is well-known."