The House Foreign Affairs Committee yesterday dealt a setback to President Reagan's hopes for a freer hand in conducting foreign policy by voting 19 to 5 to reject the administration's request to lift the ban on covert or overt assistance to rebel forces in Angola.

The administration is seeking repeal of the so-called Clark Amendment, enacted by Congress in 1976, as part of its campaign to get rid of post-Vietnam restrictions that it regards as inhibiting the president's ability to deal with unpredictable situations in the foreign policy area.

The Clark Amendment, named for former senator Dick Clark of Iowa, heads the list of those legislative restraints that the administration wants eliminated.

A senior State Department official said in an April 30 background briefing that the administration has no intention of trying to undermine the communist government in Angola by aiding its rebel adversaries. Still, the administration has made clear it wants to do away with the Clark Amendment as a symbolic signal that the United States is prepared to turn away from its post-Vietnam disenchantment with foreign involvements and back Reagan's efforts to project a bold new U.S. image.

So far, however, the president's desires have been making little headway in Congress. Both the House committee and the Senate Foreign Relations Committee have turned aside administration objections to vote for restrictions on U.S. military assistance to El Salvador.

In addition, the House committee yesterday voted for a fiscal 1982 foreign aid bill of $6.026 billion, $654 million less than what Reagan had sought. It made these cuts primarily in the area where Reagan and Secretary of State Alexander M. Haig Jr. had proposed increases -- that of foreign military assistance.

Specifically, the committee eliminated, in the case of almost every country except Israel, the administration's request to carry out much of its foreign military sales program by forgiving repayment or granting the recipient nations especially favorable interest terms. It also shaved the administration's request for a $250 million economic support contingency fund for use in military trouble spots to $100 million, and cut a parallel request for a military grant contingency fund from $150 million to $25 million. r

In another move that went against administration wishes, the committee followed the lead taken Monday by the Senate Foreign Relations Committee and voted to specify that U.S. military aid to the military regime in Argentina be contingent on a presidential certification that Argentina is making progress in improving its human-rights record.

However, the committee's most attention-getting action was its vote, with virtually no debate, to spurn the request for lifting the Clark Amendment. Rep. Howard E. Wolpe (D-Mich.), chairman of the Africa subcommittee, urged that the ban be retained on the grounds that repeal would increase the Angolan government's reliance on the 20,000 Cuban troops in that country and harm efforts to reach agreement on gaining independence for neighboring Namibia from South Africa.

The Cuban troops are helping to protect the Angolan government against rebel forces led by anti-Marxist Jonas Savimbi. The Reagan administration, which is about to undertake a new effort to resolve the Namibia conflict, has stated it wants the Cubans out of Angola as part of its attempt to contain communist influence in Africa.

However, supporters of the amendment have argued that repealing it at this time will raise suspicions throughout black Africa that the United States is trying to help the Angolan rebels. Such suspicions, they contend, will make the black African countries reluctant to cooperate in the new push for a Namibia settlement.