President Clinton urged Israeli Prime Minister Ehud Barak and Palestinian leader Yasser Arafat today to seize the "moment of opportunity" and move swiftly toward agreement on the toughest unresolved issues of the Oslo peace accords.

The president held separate meetings with Barak and Arafat--with no aides present--after arriving here for memorial ceremonies honoring assassinated Israeli prime minister Yitzhak Rabin, who signed the Oslo agreement with Arafat in 1993. Among other world leaders here is Russian Prime Minister Vladimir Putin, who will meet with Clinton on Tuesday.

Despite a serious case of jet lag--he slept barely two hours on the transatlantic flight--the president spent much of a long day nudging the Middle Eastern leaders toward agreement, even though he cautioned reporters not to expect "some sort of major announced breakthrough."

On Tuesday, Clinton is to meet with Barak and Arafat together in the hope that he can accelerate their next round of talks on such difficult issues as the borders of a Palestinian state and the status of the disputed city of Jerusalem.

In the back-and-forth of negotiating sessions here today, Barak suggested at one point that it might be fruitful for all the principals in the talks to gather for another meeting at Camp David--possibly as early as January. But White House officials moved quickly to play down that suggestion, and Barak himself seemed to back away from it later in the day.

Tonight, King Harald V of Norway held a lavish dinner at the royal palace in honor of Rabin. The late Israeli leader shared the Nobel Peace Prize with Arafat in 1994 for his work on the Oslo accords, which were completed during months of secret Israeli-Palestinian negotiations here under Norwegian auspices. The peace deal was a gamble on Rabin's part, and he paid for it with his life. He was assassinated by an Israeli nationalist four years ago this week.

For all Clinton's efforts today, the most forceful appeal came from Rabin's widow, Leah. Speaking at the memorial dinner, she recalled the night her husband was killed. He had addressed a huge crowd in Tel Aviv that was cheering the peace accords, she said, and "I saw my husband euphoric maybe for the first time in his whole life." Hours later, he was dead.

"I'm now turning to you, Chairman Arafat," she went on. "And to you, Prime Minister Barak. . . . The right formula to accomplish what my husband started is now up to you. Is it too much to ask for?"

In Israel today, the newspaper Haaretz offered a detailed report--evidently leaked by Barak's government--on Israel's negotiating position in the next round of peace talks. It said that Israel would be willing to recognize an independent Palestinian state in return for security guarantees.

As the home of the Nobel Peace Prize, this hilly city at the tip of the icy Oslofjord is accustomed to hosting VIPs from around the world. But Clinton is the first incumbent U.S. president ever to visit Norway, and his arrival early today prompted unprecedented security precautions.

All the local newspapers ran the same front-page photograph, showing a policewoman on Oslo's main street holding an automatic rifle.

That's a shocking image in a tranquil society where neither police nor anybody else carries a gun in normal circumstances.

Still, Clinton got a warm reception in Norway, a nation that seems to have no major argument with the United States at the moment. The bilateral U.S.-Norway sessions on Clinton's schedule turned into one long love feast.

Over lunch at the Royal Palace, Harald, 62, recalled that he was sent to the United States in his childhood after the Nazis invaded Norway.

One of his foster homes was the White House, the king said today in a voice filled with nostalgia, and "one thing I remember quite clearly is standing right behind President Roosevelt when he was sworn in for his fourth term."

Clinton responded in kind, recalling his visit to Norway in 1969 as a graduate student. "I fell in love with this country," the president said.

Recalling the mass migration from this country to the United States in the 19th century, the king pointed out that "almost every Norwegian has a relative in America."

Clinton then ticked off the names of several famous Norwegian Americans, including Knute Rockne, James Cagney, former chief justice Earl Warren and former vice president Walter F. Mondale.

Tuesday's schedule includes a formal memorial service for Rabin, followed by Clinton's meeting with Barak and Arafat.

Shortly before he flies back to Washington, the president is to meet with Putin. A White House spokesman said Clinton will tell the Russian premier that the United States is "very concerned about the increasing level of violence" in Russia's military offensive in the separatist southern region of Chechnya.

CAPTION: President Clinton and Norwegian King Harald V greet schoolchildren at the Royal Palace before attending a ceremony honoring slain Israeli prime minister Yitzhak Rabin.

CAPTION: Palestinian leader Yasser Arafat, left, and Israeli Prime Minister Ehud Barak shake hands before talks in Oslo on the Middle East peace process.