Prime Minister Benjamin Netanyahu sought Tuesday to temper expectations about a deal to exchange a captured Israeli soldier for hundreds of Palestinian prisoners, saying “There is still no deal, and I do not know if there will be one.”

Addressing the fears of some Israelis that a swap would boost the standing of Hamas, Mr. Netanyahu said the authorities would “not be sparing with a public discussion. We will not do it as a fait accompli,” news reports said.

He spoke after the industry and trade minister, Binyamin Ben-Eliezer, said a deal was “moving toward completion in the very near future.”

Expectations of a swap in the coming week, a move with far-reaching implications not only for stalled Middle East peace talks but also for a range of regional relations, have been raised by a round of meetings in Cairo sponsored by the Egyptian government, and by a growing number of statements by Israeli, Palestinian and Egyptian officials.

“Those who don’t know can talk,” Dan Meridor, Israel’s intelligence minister, said Monday on state radio. “Those who know should keep silent.”

The emerging agreement, should it be approved, would trade Staff Sgt. Gilad Shalit, who was seized by Hamas and other Palestinian militants in a cross-border raid and taken to Gaza in June 2006, for hundreds of Palestinians in Israeli prisons, including many convicted of organizing suicide bombings and other acts of terrorism.

Hamas and Israeli officials said the deal could include Marwan Barghouti, one of the most popular leaders in the West Bank, widely seen as a potential heir to the current Palestinian president, Mahmoud Abbas. An Israeli court gave Mr. Barghouti five life sentences in 2004 for involvement in the killing of Israelis.

“There is a serious chance Barghouti will be released,” said Danny Danon, deputy speaker of the Israeli Parliament and an important member of Mr. Netanyahu’s Likud party, in an interview in his office.

But a deputy prime minister, Silvan Shalom, told the BBC’s Arabic-language service that Mr. Barghouti would not be part of any trade.

Mr. Barghouti was elected from prison to a top Fatah leadership post this past summer. Some say he is a rare leader who could unify the Palestinian people.

While prisoner exchanges have occurred in the past, a deal now would have unusual potential to allow the Israelis to shift some policies toward Palestinians — as well as to unleash new violence against Israel — making an exchange the topic of anguished debate in the country. It is also being passionately debated among Palestinians because of the deep division between Hamas and its rival, the Palestinian Authority, which is dominated by Fatah.

Most Israelis have followed the fate of Sergeant Shalit, who was a corporal when captured but has since been promoted, as if he were their own son. A bespectacled and boyish-seeming 23-year-old, he was last seen in a video released last month, looking thin and wan. His picture and name are everywhere in Israel, and his fate is the topic of endless concern and prayer. Most Israelis perform mandatory military service, and the government goes to sometimes extraordinary lengths to bring home soldiers, or their remains.

Yet the release of legions of violent fighters and the chance that Hamas would gain politically over the Palestinian Authority have made this a complex negotiation for the Israelis.

“From our point of view, this will lay the ground for the next 9/11,” Yossi Mendellevich, an engineer whose 13-year-old son, Yuval, died in a bus bombing in Haifa in 2003, said by telephone. “We know they will not turn to macramé and painting,” he said of the security prisoners to be released.

“This will give the tail wind to all those in the Arab world who believe the way to defeat Israel is through terrorist activity,” Mr. Mendellevich said. “It will lead to the kidnapping of another soldier and to the next release and so on. What will be the end?”

Yaakov Perry, former head of the Shin Bet internal security agency, told Israel Radio that while a real risk existed, “the past has shown that some of the prisoners do not return to terror and some portion are integrated in various operative positions.”

Israelis are also concerned by Hamas’s request that some Israeli Arabs be released, fearing that Hamas’s standing would increase among the 20 percent of Israel’s citizens who are Palestinians.

Moreover, since Hamas receives support from Iran, any boost for Hamas could strengthen a country that Israel considers the region’s greatest menace.

Among Palestinians, any prisoner release is a source of joy and relief. But this is an especially delicate moment in Palestinian politics. Mr. Abbas has vowed not to run again for the Palestinian presidency because of what he said was his frustration over Israeli and American policies. With no clear successor to Mr. Abbas and a stalled peace process, some fear that if released prisoners are seen as gifts from Hamas, Mr. Abbas and his party will suffer a severe blow. How Mr. Barghouti’s release would affect this situation is unclear.

Ziad Abu Ein, the Palestinian Authority’s deputy minister for prisoner affairs, played down the damage that a prisoner exchange credited to Hamas could inflict on the authority and Mr. Abbas.

“This is the first time that Hamas will be releasing any prisoners,” Mr. Abu Ein said in a telephone interview on Monday. The Palestine Liberation Organization, by contrast, has released “tens of thousands” over the years, he said.

He added that rather than Hamas’s gaining an advantage with the Palestinian people through a deal on Sergeant Shalit, the soldier’s capture led the people of Gaza to pay a heavy price.

He was referring, among other things, to the blockade that Israel has imposed on Gaza since Hamas took control there in 2007. The embargo, which bans nearly all commercial and human traffic between Israel and Gaza, is largely aimed at isolating Hamas because of its commitment to Israel’s destruction, and creating a contrast between conditions in Gaza and those in the West Bank, run by the Palestinian Authority.

Many governments, including that of the United States, want to end the embargo to relieve the suffering of the 1.5 million people in Gaza, especially after Israel’s invasion 11 months ago, which destroyed homes and factories. But Israel has said the embargo will not end until Mr. Shalit is free.

Therefore, if a deal is really imminent, it may also signal the possibility of some opening of the commercial crossings. Efforts to reconcile Fatah and Hamas, also being brokered by Egypt, could conceivably make progress, too.