The already-intense struggle between the United States and the government of Panamanian strongman Gen. Manuel Noriega is approaching nearly all-out conflict, with the Senate voting for sweeping U.S. sanctions and Noriega seeking to obtain financial support from the Soviet Union and Libya and to work more closely with anti-U.S. groups in Central America, Reagan administration officials said yesterday.

The Senate action early last Saturday, in a provision of the omnibus spending bill known as a continuing resolution that is intended to fund the U.S. government through next September, is among the most far-reaching sanctions ever voted against a supposedly friendly country. It requires total U.S. cutoff of virtually all economic and military aid, including aid previously voted and still undelivered; the elimination of Panama's sugar quota for export to the United States, and mandatory U.S. votes against loans to Panama in international development banks.

Senate sources said a similar provision is likely to emerge from conference with the House of Representatives, where anti-Noriega sentiment is also strong. The Reagan administration froze most of Panama's $26 million U.S. aid program in early July, although some aid already in the pipeline was permitted.

A senior State Department official said all U.S. government agencies have agreed since last spring that the "ultimate solution" to growing troubles in Panama and in its relations with the United States is the removal of Noriega from his position of power over governmental affairs.

"We're constantly reviewing the tactics" of how to accomplish this, the official said, adding that Washington has been dissatisfied with recent conditions in which the conflict with Noriega has deepened but the military leader's position remains strong.

The Panamanian government is expected to move soon to announce internal reforms in a bid to ease U.S. and domestic opposition. But Washington sources said such action is unlikely to make a basic change in either the administration or congressional consensus that Noriega must go.

The strong senatorial consensus was demonstrated by the release Monday of a staff report signed by a bipartisan group of staffers, spanning the political spectrum from Sen. Edward M. Kennedy (D-Mass.) to Sen. Jesse Helms (R-N.C.), urging that all U.S. aid be halted and all official contact with Noriega terminated.

Noriega, in a move described by a senior administration official as an effort to "tweak us," is reported to have approved landing rights in Panama for Aeroflot, the Soviet airline, and to be moving toward a service contract to provide dry-dock and other shore facilities for the Soviet fishing fleet.

A Panamanian exile source said a three-year contract was signed in August for the landing rights and some support for Soviet seamen through General Sky Shops Corp., a Panamanian corporation that the source said is owned indirectly by Noriega. The first of the twice-weekly Aeroflot flights landed at Panama City on Nov. 26, the source said.

In another move, Noriega is reported to be seeking $200 million in emergency economic aid from Libya plus a $100 million deposit by Libya in Panamanian banks to deal with a serious cash shortage. The Panamanian exile source, who declined to be named, said a first emissary had been sent to Tripoli in early November and that separate discussions were held in Panama with the Libyans. The Libyan response is not known.

In still another sign of deteriorating relations, the Panamanian ambassador to Costa Rica, David Tere, charged in a news conference in San Jose Monday that the United States is plotting to assassinate Noriega and destabilize the Panamanian government, according to news accounts there. Tere charged that some parts of the U.S. "plot" are being carried out in Costa Rica.

A senior U.S. official denied that there is any such U.S. plot. Maj. Roger Miranda Bengoechea, who recently defected from the Nicaraguan Defense Ministry, told reporters in Washington last Thursday that Nicaraguan Defense Minister Humberto Ortega had concocted a story last summer that he had obtained information about a U.S. assassination plot against Noriega. Miranda said Ortega had arranged for Noriega to be informed of the "plot" by the Nicaraguan chief of military intelligence, Ricardo Wheelock, who reported back that Noriega found the information credible.

The Nicaraguan defector also told reporters that Noriega had offered in August to supply weapons to the communist-led rebels in El Salvador if the Nicaraguan government would approve. The defector claimed that approval was given, but said he did not know whether the weapons were ever supplied.Staff writer Joe Pichirallo and researcher Michelle Hall contributed to this report.