The Quartet for the Middle East is concerned over ongoing settler violence and incitement in the West Bank, a statement following a meeting of the group's foreign ministers said on Wednesday, adding that negotiations, not settlement expansion, would solve the Israeli-Palestinian conflict.

The message was released following a Washington meeting, participated by United Nations Secretary General Ban Ki-moon, Russian Foreign Minister Sergey Lavrov, United States Secretary of State Hillary Rodham Clinton and European Union High Representative for Foreign Affairs and Security Policy Catherine Ashton, as well as by Quartet Representative Tony Blair and by Foreign Minister of Jordan Nasser Judeh.

On Monday, Palestinian UN observer Riyad Mansour sent a protest letter to the UN Security Council, accusing Israel of systematically destroying prospects for a two-state solution to their decades-long conflict with its continuing campaign of settlement building.

Mansour said Israel's "illegal and destructive plans" to build new settlements underscore "the dubious nature" of its claims of readiness to negotiate a peace deal.

In a statement on Wednesday, the Quartet "expressed its concern over ongoing settler violence and incitement in the West Bank," calling on Israel "to take effective measures, including bringing the perpetrators of such acts to justice."

In addition, the statement said the Quartet was concerned "about unilateral and provocative actions by either party, including continued settlement activity, which cannot prejudge the outcome of negotiations, the only way to a just and durable solution to the conflict."

"The Quartet condemned rocket attacks from Gaza and stressed the need for calm and security for both peoples," the statement added, underscoring "the importance of continued steps to address the needs of Gaza’s residents, and welcomed the Israeli Government’s approval at the AHLC meeting of UN priority infrastructure projects in Gaza."

The statement reminded "both parties of their obligations under the roadmap," reiterating its call to avoid actions that undermine trust and to focus on positive efforts that can strengthen and improve the climate for a resumption of direct negotiations on the basis of the Quartet’s September 23 statement."

Wednesday's missive also encouraged what it called the Palestinian Authority's institution-building activities, saying that "the Quartet called on the international community to ensure the contribution of $1.1 billion in assistance to meet the Palestinian Authority’s 2012 recurrent financing requirements."

State Department spokeswoman Victoria Nuland said the meeting "very productive", but cautioned that the group would have to "take it one step at a time".

"At the moment what we're trying to do is get the parties back into direct contact with each other. They've talked about some positive steps that they want to make," she said. 

"The statement speaks not only of the Quartet principals' commitment to their own principles from September, but they also talk quite a bit in the statement about the need for continued international support for the institution-building projects of the Palestinian Authority," Nuland said of the Quartet meeting.

"What we're talking about is concern about security on the ground, the importance of all sides maintaining security, and also about the importance of funding Palestinian institutions so that they can continue to provide services to the Palestinian people. Our position here has been that it's very important to empower moderate politicians within the Palestinian political system and to have them be able to deliver services to the Palestinian people as a way of deterring radicalism," she added.