With the words, "It is yours," former president Jimmy Carter symbolically turned over the Panama Canal to Panama at a ceremony here today, marking the end of American control of the 51-mile waterway that for nearly a century represented the projection of U.S. power in Latin America.

Although the United States will not relinquish ownership of the canal officially until Dec. 31, today's ceremony was scheduled to avoid any conflicts with millennium activities. It was the culmination of the transfer launched by Carter in 1977 with the signing of the Panama Canal Treaties.

"Today we come together with mutual respect to acknowledge without question the complete sovereignty of Panama," Carter, who represented the United States, told a gathering of dignitaries at the canal's Miraflores Locks that included six Latin American presidents and King Juan Carlos of Spain.

The festivities were overshadowed by the absence of President Clinton and Secretary of State Madeleine K. Albright, both of whom stayed away from a ceremony that focused attention on the turnover of the strategic waterway--a move that remains highly unpopular among American conservatives.

Speaking under a light rain, Carter said the original canal accords signed at the birth of Panama as an independent country in 1903 were unjust and that the United States "did not understand clearly enough that the arrangement defined a certain element of colonialism."

Panamanian President Mireya Moscoso heralded Panama's assumption of the canal "trophy" as a consolidation of her country's sovereignty. She went out of her way to reassure other countries and international shippers that the interoceanic waterway, which is transited by 14,000 vessels a year, would be well maintained and improved under Panamanian control and run under a "code of ethics."

"Our final objective is to guarantee safe, efficient and uninterrupted operation of the canal to satisfy our customers and to benefit our country," she said.

The 29-member U.S. delegation was headed by Carter, who signed the treaties with Panamanian leader Gen. Omar Torrijos to hand over the canal, as well as 360,240 acres of land. The agreements, which also called for the eventual withdrawal of all U.S. troops from Panama, were unpopular in the United States but were ratified by a one-vote margin in the Senate in September 1978.

Clinton has not said why he opted to skip today's ceremonies, but the White House denied that U.S. conservative opposition to the transfer played a part in the president's decision. "This decision is not made based on the politics," White House spokesman Joe Lockhart told reporters in Washington.

Albright was to have represented the United States but remained in Washington because of the start of peace talks Wednesday between Israel and Syria.

U.S. conservatives have criticized the handover of the canal--which cost the United States more than $350 million and 5,600 lives to complete in 1914--saying Panama has no army and that the canal's security could be vulnerable to left-wing rebels in neighboring Colombia who have launched incursions into southern Panama. This concern was highlighted on Sunday, when hundreds of rebels attacked a Colombian navy base on the Pacific coast 15 miles from the border with Panama, killing at least 34 marines, one policeman and a civilian.

Critics also have contended that China is seeking to control the waterway through the Hong Kong-based Hutchison Whampoa Ltd., which operates cargo terminals at both ends--assertions that the White House and the Pentagon have dismissed. Others have expressed concern that the canal may be mismanaged and fall into decline, becoming a vehicle for corruption and patronage.

The Panamanian government has undertaken several measures to insulate the canal from such abuses, including a 1994 constitutional amendment making the Panama Canal Authority an autonomous body.

Carter addressed the treaties' critics in his remarks today. "In my country and in this one there were demagogues who exaggerated problems and spoke about catastrophic events. There are still some in my country spreading false stories about security of the canal," Carter said, standing in front of a line of large container ships.

The transfer treaty permits U.S. intervention if the canal's neutrality is threatened. In a statement in Washington, Clinton expressed "a continuing commitment" to the canal's security and a determination that the waterway will remain open.

The transfer of the canal, as well as surrounding properties and a number of military bases, will give this country of 2.8 million people full sovereignty over all its territory for the first time since the United States helped it win independence from Colombia in 1903.

Noting how the United States has operated the canal in what amounted to "state socialism," Carter said Panama now faces the challenge of bringing free enterprise to the waterway and running it on a for-profit basis. "It is yours," a smiling Moscoso recalled Carter telling her today after they signed a document marking the transfer.

The ceremony was full of fanfare as Carter, Moscoso and the other dignitaries were brought ashore at the locks on the Pacific Ocean side of the canal aboard a "mule," a large engine on railroad tracks that tows ships into the locks. Rows of flags flapped in the breeze as a marching band played.

The United States, which is the largest customer of the canal, is expected to keep a close eye on the operation and security of the waterway, which provides a vital commercial link between the Pacific Ocean and the Caribbean. With all but a handful of U.S. troops gone from Panama--there were about 10,000 here when the treaties were signed--increased drug trafficking has been a major U.S. concern. The Pentagon has transferred the headquarters of its Southern Command from Panama to Miami.

Last year, Washington and the administration of former Panamanian president Ernesto Perez Balladares failed to reach an agreement that would have allowed the United States to maintain a regional anti-drug center here. Moscoso does not seem keen on the idea either.

The handover has been smooth for the most part, largely because Panamanians have been operating the canal for years. Its administration has been Panamanian for the last 10 years, and more than 70 percent of the canal's managers are Panamanian, as are the overwhelming majority of its floating equipment operators.

The canal, which is Panama's top economic resource after the Colon free-trade zone on the Caribbean, is being turned over to Panama in good operating and financial condition. Several modernization projects are also underway. These initiatives, costing about $1 billion, include the widening of the Gaillard Cut, the narrowest part of the canal, so it will be able to accommodate two-way traffic.

At least for the time being, shipping industry officials expressed confidence in Panama's ability to run the canal as well as, if not better than, the United States, but they stressed the need to enforce the laws designed to ensure the canal's autonomy.

"The transfer is just a change of flag for us; we do not see any reasons for concern," said Jurgen Dorfmeier, president of Boyd Steamship Corp., a major shipping agent here. "If the canal closes tomorrow, the shipping industry will continue to live, but the canal is all that Panama basically has, along with the free-trade zone. And one thing is for sure: Panamanians are not suicidal."

CAPTION: Panamanian President Mireya Moscoso shakes hands with former president Jimmy Carter after they signed the document transferring canal to Panama.