UNITED NATIONS, Aug 16 (Louis Charbonneau/Reuters) - The so-called Middle East Quartet of the United States, Russia, the European Union and the United Nations on Tuesday said they were alarmed by Israel's latest announcements about new settlement plans.

Israel announced on Monday approval for building 277 homes in a West Bank settlement, despite U.S. and international pressure to curb expansion on occupied land and as Palestinians prepare for a statehood bid at the United Nations.

The Quartet is greatly concerned by Israel's recent announcements to advance planning for new housing units in Ariel and East Jerusalem, the mediating group said in a joint statement.

The Quartet added that unilateral action by either party (Israel or the Palestinians) ... will not be recognized by the international community.

Jerusalem in particular is one of the core issues that must be resolved through negotiations between the parties, which underscores the urgent need for the parties to resume serious and substantive talks, the group said.

It added that resuming bilateral peace talks was the only way to a just and durable solution to the conflict.

The United States said on Monday that it found reports of new Israeli settlement building plans deeply troubling and counterproductive to the U.S. effort to revive Israeli-Palestinian peace negotiations.

For months the Quartet members have been negotiating a statement to push the reluctant Palestinians to return to the negotiating table with the Israelis, despite their anger at Israel's refusal to halt settlement activity on occupied territories the Palestinians want for a future Palestinian state.

So far, diplomats say, the Quartet members have been unable to reach a consensus due to disagreements about the framework for any resumption of stalled talks between the two sides.

Further complicating matters, Palestinian President Mahmoud Abbas has announced that he would present an application for U.N. membership for the state of Palestine to U.N. Secretary-General Ban Ki-moon in September.

Palestinian officials have presented the plan as a move toward leveling the playing field with Israel in future negotiations. The Palestinians began talks with Israel two decades ago with the aim of establishing an independent state.

Israel has condemned the U.N. bid as an attempt to isolate it and undermine the legitimacy of its own statehood. Washington also opposes the Palestinian U.N. membership bid. (Editing by Mohammad Zargham)