President Clinton flew here today for the third time this week in an effort to energize Syrian-Israeli peace talks that once again appear to have stumbled on procedural disputes and mutual mistrust.

After his helicopter alighted in a baseball field in this picturesque town on the Potomac River about 4:15 p.m., Clinton immediately traveled by motorcade to the Clarion Hotel and Conference Center for separate meetings with Israeli Prime Minister Ehud Barak and Syrian Foreign Minister Farouk Charaa.

In a briefing this evening, State Department spokesman James P. Rubin described the sessions as "good and constructive" and said the pace of the talks had accelerated from "chugging" to "trotting." But he gave no indication that the Syrians and Israelis had resolved their latest dispute.

Clinton left tonight for Washington at 10 p.m., and officials said he planned to return here Friday morning.

On its face, the snag seems trivial, centering on the meeting schedule of technical committees formed to address the main points of contention between the two long-time enemies. Israeli officials want to convene meetings on security arrangements and water rights; the Syrians want to talk about a future border.

But in fact, the dispute is more than procedural. Israeli officials say they cannot give an answer to Syria's main demand--full withdrawal from the Golan Heights, captured by Israel in 1967--until they know more about Syria's willingness to agree to demilitarized zones, early warning stations and other security arrangements.

The Syrians argue the reverse, saying it is pointless to talk about security, water rights or the nature of future relations until they know whether Israel is willing to meet their core demand.

Having participated Wednesday in technical-committee meetings on security and the nature of future relations, Syrian officials have refused to participate in other such discussions until Israel agrees to formally discuss the border question in face-to-face talks, according to two people who spoke today with members of the Syrian delegation.

"They are feeling squeezed," one of those people said, adding that a Syrian delegate told him today, "It's impossible for us to go back to Damascus without a formal meeting" on the depth of an Israeli withdrawal from the Golan.

A member of the Israeli delegation acknowledged that the two sides have hit an impasse. "The issue is there's no practical progress on the talks," the official said, adding that the Israelis were willing to discuss the border issue as early as Friday if the Syrians had agreed to further committee meetings today on security and future relations.

State Department spokesman James P. Rubin played down the significance of the dispute. He said he still expects the two sides to hold face-to-face talks on the Golan border, as well as the water issue, by the end of the week. He also suggested that the two sides had made progress during separate meetings today with U.S. mediators led by Secretary of State Madeleine K. Albright.

After meeting late this afternoon with Albright and other key members of the American team, Clinton sat down with Barak for 45 minutes before heading into a session with Charaa at 8:15 p.m. This evening, Rubin described the day's discussions as "sufficiently good and constructive that they have superseded" the need for committee meetings, at least for today.

Earlier in the day, in Washington, national security adviser Samuel R. "Sandy" Berger offered a cautious assessment. "These are very difficult issues that divide the parties," Berger told reporters. "They have been at war three times since the 1940s. There are very strong views on both sides."