A report yesterday incorrectly identified the president of Afghanistan at the time of the Soviet invasion in 1979. He was Hasizullah Amin.

Congress has secretly approved another $300 million in military aid for anti-Soviet rebels in Afghanistan over the next two years, according to sources in the intelligence community.

The funding, voted late last month after several weeks of heated debate in the House and Senate intelligence committees, is in addition to secret funds already appropriated for fiscal 1986 and 1987. It is expected to be used primarily for ammunition and small weapons, but part of it may also be spent for a new ground-based antiaircraft missile system to battle Soviet helicopters.

The new funding is a major jump from the reported fiscal 1985 total of about $250 million, which at the time was reported to make up the bulk of the Central Intelligence Agency's fund for covert operations worldwide.

The additional spending has sparked concern among Democrats in both the House and Senate intelligence committees over the scope and direction of the Afghanistan program, the sources said.

"People are seeing the potential of a $1 billion-a-year program pretty soon. For the first time there's a realization of that, and there's a lot of questions about just what are the policy implications and what are we getting out of this," one highly placed source said.

Congress has been uncommonly unified in backing the Afghanistan guerrilla resistance to Soviet occupation forces, who poured into Afghanistan in 1979 in what they said was a response to a request from the Marxist government of President Babrak Karmal. Casualties have been heavy on both sides, and the current funding request was justified on grounds that the rebels need to be confident of stable supplies over the next two years.

However, critics have charged that much of the aid intended for the rebels has somehow disappeared into a maelstrom of graft and political maneuvering involving the CIA, assorted intermediaries and officials of the Pakistani government who are thought to be facilitating the transfers.

The Reagan administration launched the current debate several weeks ago with a request to reprogram $300 million to the Afghan aid program out of fiscal 1985 money left unspent in a secret Defense Department account, the sources said.

Although several members of the House intelligence committee argued that the new funding should be delayed until the mushrooming program could be evaluated, the administration pushed to obtain approval before the fiscal year ended Sept. 30 and the funds reverted to the Treasury.

The procedure avoided the need for approval by the full Congress because it had already appropriated the funds for national security purposes, the sources said. But the high-pressure approach raised some lawmakers' hackles and led to questions about the sudden discovery of so much unspent money at a time of rising congressional interest in cutting defense spending.

"The purpose of one of the meetings got lost," one participant reported. "But it became clear that the program is not going to continue at this rate of increase . . . . We support it but we can't just give a blank check."