President Reagan, repeating U.S. demands for Gen. Manuel Antonio Noriega to surrender his power over Panama and leave the country, yesterday increased economic pressure on Noriega by suspending trade preferences and holding up a $6.5 million payment due Tuesday.

"What we think should happen is that

{Noriega} should leave Panama," Secretary

of State George P. Shultz said at a White House briefing where the steps were announced.

But Shultz made clear that if Noriega gives up his leadership of the Panamanian Defense Forces and goes into exile, the United States will not drop the drug-trafficking charges on which he was indicted by two federal grand juries last month.

"He has been indicted in this country, and I'm sure the Justice Department intends to prosecute him if it can . . . . That's our position," Shultz said.

Asked why Noriega should give up his safe haven in Panama under those circumstances, Shultz replied: "Well, he ought to be thinking a little bit about the good of the people of Panama -- that's one reason."

The latest moves in the gradually escalating U.S. campaign to clamp a financial vise on the Noriega-controlled Panamanian government were made after intense debate within the Reagan administration about whether they would fan Panamanian discontent with Noriega.

Because of concern by the Pentagon and Central Intelligence Agency that too much pressure could be counterproductive, Reagan's new sanctions are aimed mainly at drying up the funds available to the Panamanian government without causing permanent damage to the economy.

Reagan, in a statement issued by the White House, directed that Panama be deprived of the preferences it normally gets on about $96 million in annual trade because of its status as a Third World country and participant in the Caribbean Basin Initiative.

He also ordered all federal agencies to inventory all payments due Panama from the U.S. government "to determine those that should be placed in escrow . . . on behalf of the Panamanian people," and he directed that the $6.5 payment, due Tuesday, be put in escrow.

That payment is part of about $80 million that the United States pays to Panama annually under the 1978 Panama Canal Treaties. Panama receives two payments of $10 million each and monthly installments of $6.5 million to $7 million.

"Further, in keeping with the spirit of our war against drugs, I have ordered that Panama be subject to intensified scrutiny by our immigration and customs services in order to apprehend drug traffickers and money launderers," Reagan's order said.

U.S. military and economic aid to Panama has been suspended since last summer. After Noriega forced the ouster last month of Panama's civilian figurehead president, Eric Arturo Delvalle, the United States continued

to recognize Delvalle, who is in hiding. The U.S. position that Delvalle is the legitimate president has enabled Noriega's opponents to block the new government, headed by Manuel Solis Palma, from withdrawing funds deposited in U.S. banks.

For that reason, Shultz explained, it was not necessary for Reagan to order American firms to stop shipping Alaskan oil to U.S. East Coast ports through a pipeline across Panama. He noted that the pipeline fees, which generate $70 million to $90 million a year for Panama, are paid into one of the U.S. accounts that currently cannot be drawn on by the Panamanian government.

Shultz, calling Reagan's statement a "powerful message" to the "illegitimate Noriega regime," appeared to be appealing to the Panamanian Defense Forces to push Noriega aside and "resume an honorable and proper role in a constitutional system."

He refused to answer questions about whether corruption is embedded in the Panamanian military and involves most of its top commanders.

Several senior officers have been named along with Noriega in the U.S. drug indictments.

Noriega, whose emissaries have asked whether the United States would drop the charges if he goes into exile, has been told that

the antidrug sentiment in Con- gress and U.S. public opinion is so strong that he can be given no assurances.