UNITED NATIONS (AP) — The Palestinians are accusing Israel of systematically destroying prospects for a two-state solution to their decades-long conflict with its continuing campaign of settlement building.

Palestinian UN observer Riyad Mansour sent a protest letter to the UN Security Council on Monday, two days before the Quartet of Mideast mediators — the US, UN, European Union and Russia — meets in Washington to discuss peace prospects.

Israeli-Palestinian talks remain stalled over Palestinian demands that Israel stop building on lands they claim. Israel has defied international pressure to freeze settlement construction.

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.