PANAMA CITY -- Panamanian strongman Gen. Manuel Antonio Noriega is casting about for ways to shore up a declining economy and mollify his domestic opponents while continuing to resist U.S. pressure against him.

Efforts by figurehead President Eric Delvalle to restore economic confidence are being dismissed by the opposition to Noriega, considered the power behind the government, as cosmetic.

In recent weeks, Noriega or his subordinates have made overtures to Libya, the Soviet Union and Haiti; expelled employes of the U.S. Agency for International Development (AID); accused the United States and Costa Rica of involvement in a plot to kill him and charged that Washington turned against him because he refused to fight Nicaragua's Sandinista government.

"I think Noriega is showing signs of desperation," said Ricardo Arias Calderon, the president of Panama's opposition Christian Democratic Party.

Since a political crisis erupted here in June, with demonstrations demanding Noriega's ouster, Panama's economy has been crippled by massive capital flight, falling government reserves and an inability to obtain new credit. While real growth in the country's gross national product was put at an annual rate of 2.5 percent for the first half of this year, the economy then declined so sharply that the overall figure for 1987 now is projected at minus 1 to 2 percent.

Deposits in Panama's banking system dropped by $8 billion from June to October, official figures show. And, according to International Monetary Fund statistics, the government's reserves fell from $244.3 million in April to $117.8 million by the end of August. A delay in paying traditional December bonuses prompted dock and electrical workers to strike briefly last week, until the government announced it would make the payments.

In response to U.S. congressional moves to cut off economic and military aid, Noriega ordered the expulsion of AID, effectively ending programs to assist the private sector. He has offered landing rights and dry-dock facilities to Soviet airliners and fishing vessels. And he recently telephoned the head of Haiti's ruling National Government Council, Lt. Gen. Henri Namphy, to express "solidarity" because, he said, both regimes face destabilization from disloyal citizens and the United States.

In another apparent reaction to U.S. pressure, Noriega recently sent a delegation to Libya to seek $200 million in emergency assistance. Although there has been no word on Libya's response, the prospect of close relations with Libyan leader Moammar Gadhafi so alarmed Panama's influential Jewish community that Noriega had to publicly reassure "our Hebrew brothers" in a Dec. 15 speech that there was "no threat of Libyan sabotage" in Panama.

The National Council of Private Enterprise last week called the approach to Libya "simply irresponsible" and warned that it could adversely affect private investment here. Expressing similar criticism, the Union of Industrialists said the move reflected the government's desperate financial situation.

On Dec. 14, the Panamanian ambassador to Costa Rica, David Pere, told a news conference that Cuban exiles supported by the U.S. embassies in Costa Rica and Panama were plotting to assassinate Noriega. Pere, an associate of Noriega, charged that the government of Costa Rican President Oscar Arias, who was abroad after having just received the Nobel Peace Prize, had acquiesced in the movement of men and arms through Costa Rica to carry out the plot.

The Costa Rican government denounced the charges, for which no proof was presented, and said it did not want Pere as ambassador.

In a speech on Dec. 16, Delvalle said the government would allow four opposition newspapers and two radio stations closed in July to resume operations by year's end, would "pardon" opposition leaders who fled the country to escape a crackdown and would name two new Supreme Court justices and give the opposition a slot on the three-member Electoral Tribunal.

While noting "some ambiguities" in the speech, the State Department called it "a positive step aimed at beginning the political changes necessary to restore full and functioning democracy to Panama."

However, opposition leader Arias Calderon called the measures "cosmetic changes to try to respond to U.S. pressures." He said the reopening of the news media was conditioned on passage of a new press law that "legalizes the repression of freedom of the press" and that the "pardon" also covers members of paramilitary groups that have killed three persons in attacks on demonstrators since June.

{In Washington, former ambassador to the United States Gabriel Lewis, who fled Panama last summer after he was accused of plotting to overthrow the government, said he was not among the Panamanian exiles who were pardoned. Lewis is directing an anti-Noriega lobbying effort on Capitol Hill.

{According to Lewis, Delvalle's pardon also excludes Roberto Eisenmann, publisher of the opposition newspaper Diario La Prensa, and columnist Guillermo Sanchez Borbon, both of whom are in exile.}

The Associated Press reported from Caracas, Venezuela:

Retired Panamanian colonel Roberto Diaz Herrera, who set off demonstrations last June by accusing Noriega of involvement in assassination and election fraud, received a presidential pardon and was freed from jail Thursday, and immediately left Panama for Venezuela, officials and relatives said.

Diaz was sentenced earlier this week to five years in prison for crimes against state security.