MOSCOW, Mar 19 (Reuters) - Middle East mediators condemned for the second time in a week on Friday Israeli plans to build new settlements in disputed East Jerusalem, but the United States suggested Israel was moving to address the issue.

US Secretary of State Hillary Clinton, in Moscow for a meeting of the Middle East quartet, said Israeli Prime Minister Benjamin Netanyahu had given a 'useful and productive' response to her concerns on the settlement issue during a telephone conversation on Thursday. She did not give details.

The quartet -- Russia, the United States, the United Nations and the EU -- issued a statement repeating its condemnation of Israel's plans to build 1,600 new housing units on land the Palestinians want for a future capital.
It also called on all parties to promote indirect peace talks between Israel and the Palestinians as part of moves towards establishing a Palestinian state in Gaza and the Israeli-occupied West Bank within 24 months.

But the mediators did not say how they could ensure their calls, which have gone unheeded in the past, would be respected.

Hours before the quartet met, Israeli aircraft struck at least six targets in the Gaza Strip in response to deadly rocket fire from the Hamas-ruled territory the previous day, which killed a Thai worker in Israel.
The quartet statement condemned the rocket fire from Gaza and called for an 'immediate end to violence and terror' but added:

'The quartet is deeply concerned by the continuing deterioration in Gaza including the humanitarian and human rights situation of the civilian population and stresses the urgency of a resolution to the Gaza crisis.'

UN Secretary-General Ban Ki-moon said he would travel from the Moscow meeting to Gaza on Sunday to see the situation on the ground there for himself.

Clinton spoke to Netanyahu on Thursday and the Israeli leader's spokesman later said he had proposed 'mutual confidence-building measures by Israel and the Palestinian Authority in the West Bank' but did not elaborate.

The Palestinians say they will not enter indirect peace talks unless Israel scraps the new settlement plans.

Clinton met her Russian counterpart Lavrov, the UN's Ban, EU foreign policy chief Catherine Ashton and Quartet Representative Tony Blair over a closed dinner on Thursday evening before Friday's formal meeting. No details of that meeting were disclosed.

The quartet was formed in 2002 in Spain to assist in mediating an end to escalating violence in the Israeli-Palestinian conflict. It last met on the margins of the UN General Assembly in September.

But its achievements so far have been meager, leading some analysts to dismiss it as an expensive club for diplomats.

Moscow had originally hoped to organize a full-scale international conference on the Middle East this year but
the lack of progress on Israeli-Palestinian peace talks forced Russia to settle instead for hosting a quartet meeting.