Congressional Democrats, seeking to help the State Department avoid a financial crisis that could disrupt U.S. foreign policy, have worked out a plan for reshuffling funds that would spare the department from having to eliminate about 1,270 jobs and close 15 overseas diplomatic posts.

Deputy Secretary of State John C. Whitehead, responding to the proposal by Sen. Claiborne Pell (D-R.I.) and Rep. Daniel A. Mica (D-Fla.), said yesterday that senior department officials are "encouraged and enthusiastic" about the plan but need more information.

Specifically, Whitehead said, the administration wants a clearer idea of whether the House and Senate Appropriations committees would support the proposal, which Pell and Mica plan to incorporate into a pending foreign affairs authorization bill. Whitehead also pointed out that the administration objects to several amendments in the authorization bill and that President Reagan may decide to veto it.

A much less hesitant response came from the American Foreign Service Association, the bargaining agent and professional organization of the Foreign Service. AFSA Vice President Evangeline Monroe, noting that the plan would permit Secretary of State George P. Shultz to use funds earmarked for construction and building rehabilitation for salaries and operating expenses, said it was in accord with appeals by department employes for the Reagan administration to "cut things, not people."

"We stand by our assertion that the department's most valuable resource is the talents of its people," Monroe said. "If the administration and the senior management of the department do not avail themselves of this opportunity, it will be a clear signal that they do not value these talents and are willing to accept the destructive impact that the planned job cuts will have on morale."

At issue is an anticipated $84 million shortfall in the operating budget for salaries and expenses that the department expects to receive from Congress for fiscal 1988. Leaders of the Democratic-controlled House and Senate say the fault rests with the administration because of its insistence that Congress vote more money for foreign affairs programs, which lack a large and clear-cut constituency, while demanding cuts in politically popular domestic programs.

To absorb the shortfall, senior department officials, under Whitehead's direction, prepared a plan of consolidations and program reductions that would eliminate about 8 percent of the department's 15,800 Foreign Service and Civil Service personnel. That caused what many senior officials acknowledge has been the severest blow to morale since the late 1940s and early 1950s, when the State Department was a target of anticommunist witch hunts.

In adopting the cry of "things, not people," department employes have called for much of the cuts to come from an ambitious embassy-security program that has been budgeted at $417 million annually for five years. However, funding for that program has been sheltered in a special appropriation separate from State Department operating funds.

Congressional leaders have made clear that they will not permit diversion of those funds because, they say, Congress approved that money in response to a high-priority administration request. They add that recommendations of a presidential commission and public perceptions that the United States faces a continuing threat from international terrorism have bolstered the need for an embassy-security program.

Nevertheless, sources said, publicity about the department's plight has caused embarrassment on both sides and helped to persuade Pell, chairman of the Senate Foreign Relations Committee, and Mica, chairman of the House Foreign Affairs subcommittee on international operations, to take a new look at the situation. Mica said yesterday, "Pell and I are going to have to ride white horses and help save the State Department from its own ineptness in dealing with Congress."

Congressional aides have identified about $187 million in the department's capital account that was appropriated in past years for various projects but not spent.

The Pell-Mica plan would give Shultz discretionary authority to transfer sufficient amounts of this money into the salaries and expenses account to cover the shortfall. The plan also would raise the fiscal 1988 authorization for salaries and expenses to $133 million.

"This is only a Band-Aid," Mica said. "There will be a new foreign policy funding crisis next year unless the administration learns that instead of blaming Congress for shortages of funds, it has to be responsive to Congress' concerns and works with Congress to find the necessary sources of funding."