TEL AVIV -- During a week in which the world was transfixed by horror in the United States, the Israeli government has adopted a new, harder-line policy in its conflict with the Palestinians.

Prime Minister Ariel Sharon has stepped up military operations in the West Bank and Gaza Strip, spurned U.S. entreaties for ceasefire talks with Palestinian leader Yasser Arafat and even criticized the makeup of the U.S.-led coalition against terrorism.

"Sharon is using the opportunity to do things that, anyhow, he wanted to do, and maybe restrained himself," Ron Pundak, a veteran Israeli diplomat and now an academic, said in an interview yesterday. "But now he doesn't need to restrain himself."

Yesterday, Israeli tanks and helicopters penetrated into the main West Bank city of Ramallah for several hours, in reaction to a shooting in Jerusalem in which one Israeli was killed and another injured. In the last six days, Israeli forces have also entered Palestinian-controlled areas in Jenin, Jericho and the Gaza Strip in similar circumstances.

As well, the Israeli military said it would begin establishing a buffer zone by the West Bank in a bid to prevent bombers from entering Israel. The zone would extend along the West Bank border from Jenin to Tulkarem.

Prior to the terror attacks on the United States, the incursions and talk of a buffer zone typically triggered strong protests from the Americans and Europeans. But in the last few days, they have almost become routine and yet have barely created a ripple internationally.

Mr. Sharon attended a special session of the Knesset yesterday to commemorate the victims of the attacks in the United States. However, he also used the occasion to express his policy differences with the Americans.

Since the terror attacks, President George W. Bush and his administration have renewed their pressure for immediate high-level talks between the Israelis and the Palestinians.

Mr. Sharon rejected the idea yesterday, saying such a meeting would give Mr. Arafat legitimacy.

On Friday, in a telephone conversation with Mr. Bush, Mr. Sharon called Mr. Arafat "Israel's Osama bin Laden."

He subsequently forbade Israel's Foreign Minister, Shimon Peres, from going ahead with a meeting with Mr. Arafat that had been tentatively scheduled for yesterday.

Some believe the sudden disappearance of suicide bombings, at least as of yesterday, is the result of a political decision by Palestinian organizations. However, there has been the usual stream of drive-by shootings, sniper fire, mortar attacks and car bombs, many of them deadly. (Also yesterday, Israel announced it had arrested two Palestinians suspected of involvement with the Aug. 9 suicide bombing at a Jerusalem pizzeria that killed 16 people.)

Nonetheless, Mr. Peres did not make a secret of his anger at Mr. Sharon's decision to cancel talks with Mr. Arafat. "Why must we become the party that refuses [to talk]?" Mr. Peres asked yesterday. "If we meet and he does not do anything [to stop the violence] then all the blame will fall on him."

Still, it is Mr. Sharon who appears to have Israeli public opinion on his side. "I want to scream at our leaders, don't miss the opportunity!" wrote the populist journalist Dudu Topaz in the newspaper Yedioth Ahronoth.

Mr. Arafat said on the weekend the stepped-up Israeli military activity is an attempt to undermine negotiations.

The Palestinian leadership has been trying desperately to regain some political initiative since the terrorist attacks. News camera operators who shot pictures of Palestinian celebrations had their footage seized and have been threatened with violence, even death. (Yesterday, Palestinian authorities returned to Western news agencies confiscated pictures and videotapes of a rally in the Gaza Strip held by the militant Islamic group Hamas.)

Meanwhile, Mr. Arafat has launched a public relations offensive, saying the Palestine Liberation Organization, through the Arab League, should join the antiterrorism coalition Mr. Bush is trying to organize. The idea has outraged Mr. Sharon.