The State Department said yesterday it wants $50 million in unallocated foreign aid money that would allow the administration to respond quickly to unexpected "important foreign policy interests" abroad.

The proposed new fund was mentioned in testimony yesterday before a Senate Appropriations subcommittee on foreign operations by Undersecretary of State Matthew Nimetz.

The request is the second of its kind to have been made within a few weeks.

Last month, Defense Secretary Harold Brown urged Congress to approve a $46 million down payment on a new fund aimed at stockpiling extra military equipment that might be needed quickly by friendly countries in an emergency, beyond the arms normally stockpiled for U.S. forces or those already on order for foreign governments.

Yesterday, Nimetz also disclosed a third such program, a requested increase in the president's so-called "draw-down" authority from $10 million to $40 million. This would let the president dig deeper into existing U.S. arms supplies to ship some abroad in an emergency.

Army Lt. Gen. Ernest Graves, director of the Pentagon's Security Assistance Agency, told the subcommittee that this new action would "complement" Brown's plan.

Nimetz told Congress that none of this is meant to get around overall levels or guidelines set by Congress, and advance notification would be given of the money's use to meet any "unanticipated, priority needs."

But both new proposals described yesterday met resistance from subcommittee Chairman Jack Garn (R-Utah). Garn said he thought Congress could act very fast if necessary in emergency situations and said that the reason draw-down authorities and other unallocated fund accounts had been reduced in the past was because of past abuses, though not necessarily by this administration.

Nimetz was testifying in support of the administration's overall $2.97 billion request for fiscal 1981 to finance security assistance programs.

Of this, $734 million would be used to finance credits for foreign military sales. Israel gets $500 million of this, with the remainder spread among 34 other countries, nine nations more than last year. Among the new proposed recipients are Egypt, Gabon, Mali, Rwanda, Senegal, Barbados, El Salvador, Honduras and Nicaragua. A further aid increase for Egypt will also be sent to Congress.

The $734 million actually finances loans worth $2.84 billion.

A second portion of the overall security assistance program will involve $105 million in direct military aid grants to three countries -- the Phillipines, Portugal and Spain, places where the United States has important overseas bases.

The program's economic support fund accounts for the bulk of the overall security assistance request at $2 billion for fiscal 1981. This would be divided among 15 countries, two more than last year. The new recipients would be Lebanon and Jamaica.

About 74 percent of the total, Nimetz said, is allocated for Egypt and Israel, with Turkey coming in third.

This is the fund category where the extra unallocated $50 million is being requested "for use in meeting unforeseen developments where small amounts of assistance can support important foreign policy interests."

Congressional sources have said this economic support fund category traditionally has had few strings on it than other forms of aid and is thus politically useful to a president for trying to gain U.S. influence in various places.

The U.S. effort to arrange expanded access to ports and airfields in Oman, Kenya and Somalia for American military planes and warships also includes providing money to these countries for the first time from the economic support fund.