The State Department yesterday revealed that $4 million in U.S. humanitarian aid has been flowing directly to rebels inside Afghanistan for almost a year.

William Schneider Jr., undersecretary of state for security affairs, said Wednesday that the United States will propose providing $4 million in open aid this year. With the previously unpublicized funds, a total of $8 million will have been programmed for Afghan rebels.

State Department Spokesman Edward Djerejian, responding to published reports that the $4 million mentioned by Schneider is the first such aid, said, "There is no change in American policy . . . and there are no new programs."

Other State Department officials and members of Congress said that although the country has been overtly sending funds to the rebels since August -- and Congress was notified, as required -- the small operation was kept so quiet that not even Schneider was aware on Wednesday of the previous aid.

"State didn't want us to talk about it because of their concern about Pakistan," said an aide to Sen. Gordon J. Humphrey (R-N.H.), a vocal advocate of the aid.

Since Soviet troops occupied Afghanistan in late 1979, Afghan refugees have been fleeing to camps in neighboring Pakistan. About $400 million in covert U.S. aid intended for the Afghan resistance is thought to have been funneled through Pakistan. But Pakistan has tried to maintain public neutrality in an effort to negotiate with the Soviet Union through the United Nations for a troop withdrawal and a nonaligned Afghan government.

Pakistani Embassy officials yesterday refused to comment.

Djerejian said one open U.S. support program goes to Afghan refugees in the Pakistani camps and has totaled more than $400 million since 1980. "The second humanitarian assistance program is administered through private voluntary organizations operating in Pakistan and is designed to meet some of the needs of the Afghan people inside their own country," he said. "We expect both of these public programs to continue in the future."

Another State Department official said the program inside Afghanistan began in August, when Rep. Charles Wilson (D-Tex.) successfully pressured the department to transfer $2 million from its refugee relief fund to the Office of Federal Disaster Relief at the Agency for International Development. Most of that was spent by the International Red Cross along the Pakistani border for food, medicine and ambulances, the Humphrey aide said.

Under pressure from Wilson, Humphrey and other lawmakers, President Reagan in February authorized another $2 million from State Department discretionary funds, which went to Afghanistan under the "Cash for Food" program.

Reagan also approved a search for another $4 million from unspent program funds. Those funds were located May 2 in unspent aid planned for Syria, and will be sent shortly, the State Department official said.