Syria and Israel plunged into the real business of peace negotiations today, as President Clinton traveled to this historic college town for the opening of talks aimed at resolving one of the Middle East's most protracted and dangerous conflicts.

Israeli Prime Minister Ehud Barak and Syrian Foreign Minister Farouk Charaa arrived early this morning at the Clarion Hotel and Conference Center, a modern brick edifice that will serve as the venue for the open-ended talks. They were joined by Secretary of State Madeleine K. Albright and later by Clinton, who met separately with Barak and Charaa.

Later in the evening, however, a planned three-way meeting was canceled, State Department spokesman James P. Rubin said, although he added that the cancellation should not be interpreted as a sign of trouble. Rubin said the meeting was put off after Albright's separate meetings with Barak and Charaa ran longer than expected.

"It's not that they were unwilling to meet each other," Rubin said.

Although the Syrian-Israeli negotiations officially resumed in Washington last month, the Shepherdstown talks mark the first time since 1996 that the two sides have dealt with the substantive issues dividing them. The talks center on Syria's demand that Israel return the Golan Heights, captured by Israel in 1967, in exchange for normal diplomatic relations and security guarantees.

U.S. officials, while generally optimistic about the prospects for a settlement, cautioned that the current round of talks is not likely to produce one.

"We do not expect to be able to achieve a core agreement in one round of negotiation," Rubin said. "I think it's fair to say that we're at a time of decision, but those decisions don't get made in an instant."

But Rubin also expressed hope for "real progress toward closing some of the gaps" and held out the possibility that the round might conclude with some sort of joint statement "to record progress." The presence of technical experts in each delegation, he added, should be taken as a sign of their seriousness.

The Shepherdstown talks are in some respects modeled after the talks at Camp David that produced an Egyptian-Israeli peace deal in 1978. U.S. officials hope to profit from the intimacy of the setting at the conference center, where the two sides will stay in the same building--some of them on the same floor--and eat meals in a common dining room.

There are few distractions in Shepherdstown, a picturesque community of 18th- and 19th-century brick homes 70 miles west of Washington. Though now a venue for peacemaking, the town saw its share of strife in the Civil War, when it was flooded with Confederate wounded from the Battle of Antietam a few miles distant.

To prevent leaks that U.S. officials say could compromise the negotiations, the talks are shrouded in secrecy--to the point that Israeli and Syrian officials agreed to surrender their cellular phones, according to Rubin. Reporters covering the event have been sequestered a short distance away at Shepherd College, a liberal arts institution founded in 1871.

Clinton was to return to Washington tonight but is prepared to come back to Shepherdstown whenever his presence is required, White House spokesman Joe Lockhart said. Albright and key members of her Middle East peace team planned to remain here throughout the talks, which have no fixed time period. Lockhart said "the parties are committed to working through this week" and are prepared to remain longer if necessary.

Following the decision by Syrian President Hafez Assad to return to the negotiating table, Barak and Charaa held two days of meetings in Washington last month, focusing largely on procedural matters. The real bargaining began today. After his helicopter landed on a baseball field here at 11:44 a.m., Clinton traveled by motorcade to the National Conservation Training Center of the U.S. Fish and Wildlife Service, where he met individually with Barak and Charaa for about an hour each, U.S. officials said. Albright also met with each delegation chief.

After Albright's meeting with Charaa broke up about 8:30 p.m., U.S. officials decided to cancel the three-way discussion and substitute another meeting between Clinton and Charaa, Rubin said. "Our reading of the tempo didn't warrant a trilateral tonight."

"The president came out of his two meetings believing they were off to a good start and both sides were serious about being here," Lockhart said, adding that Clinton considers the talks a "historic opportunity" to settle the half-century conflict.

The delegations later returned to the Clarion Hotel on the outskirts of town, where the Syrians observed iftar, the ritual evening meal with which Muslims break their daytime fast during the holy month of Ramadan.

Both sides have compelling reasons for seeking a settlement now. Assad is eager to modernize his economy and boost the chances that his son, Bashar, will succeed him. Barak wants to end the long-running war between Israeli forces and Syrian-backed Shiite Muslim guerrillas in southern Lebanon.

Yet hurdles remain. Syria insists that Israel return all of the Golan Heights, the strategic plateau captured by the Jewish state in 1967. To do so, however, could extend Syrian territory to the shore of the Sea of Galilee, Israel's main source of fresh water. Israel, meanwhile, is seeking security guarantees--including the presence of international observers on the Golan's Mount Hermon--that could prove difficult for Assad to swallow.

Both sides came to Shepherdstown equipped to deal with the nitty-gritty of such issues. Charaa was accompanied by top generals and an adviser on irrigation issues; water rights are sure to be a key part of any settlement.

Barak, for his part, was accompanied by Foreign Minister David Levy, Attorney General Eliyakim Rubinstein and Tourism Minister Amnon Lipkin-Shahak, a former chief of staff who was intimately involved in the earlier rounds of Syrian-Israeli talks.

"We would expect that as the negotiations get down to brass tacks that they will break up into smaller groupings," Rubin said.

CAPTION: President Clinton escorts Israeli Prime Minister Ehud Barak, left, and Syrian Foreign Minister Farouk Charaa to talks in Shepherdstown, W.Va.