U.S. Secretary of State John Kerry smiles at a question from a reporter during a news conference about his trip to the Middle East in Tel Aviv, Israel, on Sunday, June 30, 2013.

TEL AVIV, Israel - U.S. Secretary of State John Kerry completed a new round of shuttle diplomacy Sunday without a hoped-for breakthrough in relaunching Mideast peace talks, but optimistically said he had narrowed the gaps between Israel and the Palestinians and vowed to return to the region soon to complete his mission.

Kerry said he was working on an emerging "package" meant to bring the sides together, and said he would leave a team of aides in the region to continue the efforts.

"With a little more work, the start of final status negotiations could be within reach," he told reporters, shortly before leaving Israel for an Asian security conference in Brunei.

It was not clear how much progress Kerry had truly made. He refused to provide details of the package he is working on, and Israeli and Palestinian officials, at Kerry's request, remained mum.

Even before negotiations have begun, the gaps remain wide on simply establishing the ground rules.

Negotiations have been stalled since 2008, in large part due to Israeli settlement policies in the West Bank and east Jerusalem.

The Palestinians claim both areas, captured by Israel in the 1967 Mideast war, for a future independent state alongside Israel and have demanded that Israel stop building settlements on occupied lands before talks resume. More than 500,000 Jewish settlers now live in areas sought by the Palestinians, making it increasingly difficult to partition the land into two states.

The Palestinians also say Israel's pre-1967 frontiers should be the baseline for the final borders between Israel and a future Palestine. Previous Israeli leaders have accepted the 1967 lines as a starting point for talks. But Israel's current prime minister, Benjamin Netanyahu, while endorsing the idea of a Palestinian state, has refused the Palestinian demands, saying talks should begin immediately without any preconditions.

Netanyahu has ruled out a return to the 1967 lines, saying it would threaten Israel's security and noting the Jewish people's biblical connection to the West Bank. He also rejects any division of the holy city of Jerusalem, home to sensitive Christian, Jewish and Muslim holy sites.

His tough line and the continued construction of settlements have raised Palestinian accusations that he is not serious about pursuing peace.

The Palestinians also seek the Gaza Strip for their state. Israel, which captured Gaza in 1967, withdrew in 2005. Hamas militants subsequently overran the area.

Kerry was on his fifth visit to the region since taking office early this year. Starting Thursday night, he shuttled between Amman, Jordan, Jerusalem and Ramallah, West Bank, holding three meetings each with Palestinian President Mahmoud Abbas and Israel's Netanyahu.

Their talks were long, sometimes stretching into the wee hours of the morning. His last meeting with the Israeli prime minister and his advisers ended after 3 a.m. Sunday. Afterward, Kerry took a pre-dawn stroll in Jerusalem with senior advisers. Kerry, the sleeves on his white shirt rolled up, walked with a security escort to a park near the hotel, gesturing and talking with his top advisers on the Mideast peace process. Just hours later, he traveled by convoy to Ramallah for one last meeting with Abbas, cancelling a trip to Abu Dhabi to extend his work with Israel and the Palestinians.

Addressing reporters at Israel's international airport, an exhausted Kerry, running on adrenaline, said he would have stayed longer if he did not have to attend the international conference.

"I am very positive," he said. "I also know progress when I see it, and we are making progress," he added.

He said both Netanyahu and Abbas had asked him to return to the region - on what would be his sixth visit. But he declined to disclose, even broadly, the main elements of the "package" being pursued to restart talks.

Kerry said it was best not to float ideas for others to "tear apart, evaluate and analyze." He said he would not have agreed to leave his staff in place if he didn't think it was possible to flesh out a "serious" framework for restarting discussions.

"I think this is worth it, folks," he told reporters. "Obviously, the work has to be completed. People have to make a few choices still. But the gap has been narrowed very significantly."

A Palestinian official who was briefed on Kerry's efforts said the package would likely include, as a goodwill gesture, the release of some Palestinian prisoners held by Israel. He said the Palestinians were told that Netanyahu is prepared to restrain settlement construction and to discuss the 1967 borders, without any promise to withdraw to those lines. The official spoke on condition of anonymity because he was not authorized to discuss the matter with the media.

The emerging deal is also expected to include large amounts of international aid to the Palestinians; Israeli agreement to allow the Palestinians to launch new development projects in the West Bank; and Palestinian pledges to halt their campaign of seeking recognition of their independence in international bodies before there is a peace agreement.

Over Israeli and U.S. objections, the Palestinians last year won upgraded observer status at the United Nations, and they have threatened to pursue war crimes charges against Israel if peace efforts remain stalled.

Israel's Channel 2 TV, citing anonymous Israeli officials, said there had been progress, but sticking points remained in the areas of settlements, prisoners and borders. It said Kerry was expected back in a week or so and was aiming to restart talks before the Muslim holiday of Ramadan begins early next week.

Addressing his Cabinet on Sunday, Netanyahu showed little signs of bending.

"We are not putting up any impediments on the resumption of the permanent talks and a peace agreement between us and the Palestinians," he said.

At the same time, he said, "We will not compromise on security, and there will be no agreement that will endanger Israelis' security."

He added that any agreement would be presented to the public in a referendum.

Critics have said such a step would merely add an additional obstacle to implementing any deal, which would require a broad pullout from the West Bank.

Following Sunday morning's meeting in Ramallah, the chief Palestinian negotiator, Saeb Erekat, reported progress but said gaps remained.

"I cannot say we have a breakthrough," he said. "All I can say once again is no one benefits more from the success of Secretary Kerry than the Palestinians, and no one stands to lose more from its failure than Palestinians."

As Kerry strolled to the tarmac Sunday, his top Mideast adviser patted him on the back, but both knew the job was not finished.