U.S. President Barack Obama and Israeli Prime Minister Benjamin Netanyahu speak outside the Oval Office of the White House on Wednesday. Obama reiterated Washington's 'unwavering' support for Israel's security in the face of ongoing violence. (Pablo Martinez Monsivais/Associated Press)

U.S President Barack Obama called the resumption of direct talks between Israeli and Palestinian leaders "a moment of opportunity that must be seized."

Obama spoke after meeting separately with Israeli Prime Minister Benjamin Netanyahu and Palestinian President Mahmoud Abbas at the White House Wednesday.

The two are to meet for their own talks on Thursday. These will be the first direct talks between the leaders in nearly two years.

"Our goal is a two-state solution," said Obama, adding that the process could take up to a year. "It is in the national interests of all involved, including the United States, that this conflict be resolved."

Obama said he knows that passions run deep and that he is under no illusion that it will be easy to reach agreement.

Netanyahu said his nation desires a lasting peace, not an interlude between wars.

"President Abbas, you are my partner in peace. That peace must be anchored in security," Netanyahu said.

Abbas urged Israel to freeze settlement construction in areas the Palestinians want as part of their new state, and to end its blockade of Gaza, which is controlled by the militant Hamas movement.

"We will spare no effort and we will work diligently and tirelessly to ensure these negotiations achieve their cause," Abbas said, as translated into English.

At an earlier press conference Wednesday, Obama said the U.S. is "unwavering in its support of Israeli security" in the wake of the killing of four Israelis in the West Bank.

"We are going to push back against these terrorist activities," Obama said. He spoke alongside Netanyahu after the two met privately in the Oval Office.

Israeli ZAKA rescue service members and police examine the vehicle that carried four Israelis shot to death Tuesday near the West Bank settlement of Kiryat Arba, near Hebron. (Ronen Zvulun/Reuters)

The Israelis were shot dead Tuesday evening while travelling in a vehicle near the West Bank city of Hebron.

Hamas militants, who oppose the talks, claimed responsibility for the attack, calling it a "heroic operation."

Obama said Hamas needs to know that the violence won't stop the U.S. from seeking peace in the Middle East.

Netanyahu thanked Obama for his support in the face of such "savagery and brutality," from those who "trample human rights into the dust,' and "butcher everything they oppose."

Netanyahu said Wednesday's talks were "open, productive and serious in the quest for peace," and also included security arrangements "to roll back this kind of terror." He did not specify what those arrangements were.

Abbas also condemned the "hateful attack."

Although Obama, Netanyahu and Abbas were optimistic about the talks, Rueven Hazan, an Israeli political scientist, warned that both sides are limited by internal politics.

"There's nobody there willing, ready and able to make the concessions that are necessary to move this process," he said.

"Unless we're in for a big surprise, this is a festival for two or three days. We will then get bogged down in negotiations — and hopefully that's all that we'll get, and not a wave of violence."

Israeli settler groups have said they'll defy an Israeli ban on new construction in the West Bank in response to the attack, an issue that is seen as one of the first major challenges for negotiators.

Palestinians crack down

Palestinian security forces arrested more than 150 Hamas members early Wednesday in a sweep throughout the West Bank after the Islamic militant group claimed responsibility for the settlers' deaths.

A Palestinian security official, speaking on condition of anonymity under official guidelines, confirmed a crackdown was under way but gave few details. He said the assailants from the shooting had not been found.

During a visit to a West Bank army base, Israel's defence minister, Ehud Barak, called on residents to show restraint.

"We are in the midst of a long struggle for our right to live in security in a peace agreement with our neighbours," he said.

With files from CBC's Margaret Evans and The Associated Press