Secretary of State Cyrus R. Vance, in a departure from his appeals in previous years, placed heavy emphasis on competition with the Soviets as he asked Congress yesterday to approve an $8 billion U.S. foreign aid program for the coming year.

Testifying before the House Foreign Affairs Committee as the leadoff witness for the annual foreign assistance bill, Vance repeatedly stressed the need to "compete effectively" with the Russians in the Third World in view of the "challenge" represented by the Soviet invasion of Afghanistan.

Vance's presentation drew expressions of support from the legislators, tempered with questions about specific priorities and some reservations about arms aid to such nations as Egypt and Pakistan.

Suprisingly, in more than two hours of inquiry on dozens of issues, the lawmakers did not ask a single question about the status or prospects of the U.S. hostages in Iran nor about U.S. relations with that country.

The anti-Soviet justification reminded Capitol Hill veterans of the early days of foreign aid, when large assistance programs with heavy military emphasis were popular with Congress and the public. In recent years, the aid program has been justified largely on humanitarian grounds and in terms of long-range U.S. economic and political interests.

Vance said that in the present circumstances, U.S. emphasis on security measures is "necessarily growing," but he also said that "our commitment to help meet economic and human needs remains just as strong."

Although the proposed legislation has not been actually sent to Congress yet, congressional sources said they expect the authorization for arms sales on credit to be raised about $400 million from the previous year.

One of the items holding up submission of the bill is the aid program for Pakistan. The Carter administration has offered Pakistan $400 million in economic and military aid over two years. Vance indicated that, despite Pakistani suggestions that this is "peanuts," the United States will not increase the overall sums it will request for Pakistan in these two years.

Several of the legislators asked questions about the meaning and practical effects of President Carter's State of the Union commitment to use force, if necessary, to prevent an outside power from gaining control over the Persian Gulf, Rep. Dante B. Fascell (D-Fla.) said that although European and Japanese allies are much more dependent on oil from the Persian Gulf, the United States obtains about 17 percent of its oil from there. "Our vital interests are affected, but it's not a cause to go to war," said Fascell.

Vance said the overall aid request is "austere in the light of the challenges we face." In response to numerous questions about the specific amounts of aid planned for various nations, he said the balancing of priorities was a difficult and vexing job.