State Department officials are engaged in a battle with Defense Department civilians who want to expand the Pentagon's role in humanitarian assistance programs in Central America, according to sources inside the government.

Current laws prohibit the Pentagon from conducting humanitarian activities, including transportation of donated supplies on otherwise empty military aircraft, except when requested and funded by the State Department or the Agency for International Development.

The latest clash took place over an amendment to the fiscal 1985 defense-spending bill which would have given the defense secretary authority to transport humanitarian assistance to Central America on a space-available basis.

A House-Senate conference committee approved authority for the Pentagon to use military aircraft to deliver goods and supplies from private groups for humanitarian assistance. But it gave the State Department responsibility for determining need and collecting the materials.

The legislators also prohibited delivery of such supplies to groups or individuals "engaged in military or paramilitary activity," such as the contras fighting the Nicaraguan government.

Pentagon interest in removing these constraints has grown over the past year, in light of the increase in requests for transportation assistance from conservative organizations seeking to send aid to groups fighting in El Salvador and Nicaragua.

According to government sources, the Pentagon also has been under pressure to expand humanitarian and civic action programs as it steps up its military activities in Central America and the Caribbean.

But State officials want to maintain control over the use of Pentagon aircraft to deliver aid and prevent the Defense Department from initiating operations. "These activities have serious foreign policy implications," one State official said last week.

Beginning in January, a Defense Department task force conducted a six-month study of humanitarian aid and civic action programs, coordinated by Undersecretary for Policy Fred C. Ikle.

It recommended that the Pentagon appoint a coordinator for humanitarian programs and look for ways to expand such activities, including closer cooperation with State, AID and U.S. embassies. It also recommended that the military seek congressional authorization to run such operations.

These recommendations did not draw unanimous support from all elements of the military. The Air Force, the Navy and the major theater commanders in the Pacific, Atlantic and Europe did not support building up the program, according to sources.

On June 19, one week after the task force's report was sent to Defense Secretary Caspar W. Weinberger, Sen. Jeremiah Denton (R-Ala.) introduced the amendment to the fiscal 1985 defense-spending bill.

The amendment called for the defense secretary "to consult" with the secretary of state before transporting any goods. It passed the Senate without debate, after Denton declared that "it has the support of the Department of Defense and the White House."

The language drew private criticism from State Department officials and public opposition from liberal groups who feared that it would open a channel for supporting the contra forces in Nicaragua. A letter opposing the amendment was signed by a coalition of organizations, including the American Friends Service Committee.

The conference committee rewrote it to give State continued control over the program, leaving matters about where they were when the year's activities began. However, the Pentagon is expected to again try to expand its role.