JERUSALEM, Sept 24 (Reuters) - Internationally popular Israeli authors Amos Oz and David Grossman called for ceasefire negotiations with Hamas Islamists in a newspaper advertisment published on Monday.

In a position backed by the West, Israel has said there can be no dealings with Hamas, which took over the Gaza Strip in June, until it recognises the Jewish state, renounces violence and accepts existing Israeli-Palestinian accords.

Public calls for a change in government policy on Hamas have been rare and Prime Minister Ehud Olmert has been under pressure from the right-wing to hit the group hard through a military operation in Gaza.

"The on-going Qassam rocket fire from the Gaza Strip is intolerable," said the advertisment published in the left-wing Haaretz daily and signed by Oz, Grossman and 11 other Israeli intellectuals.

"Israel has negotiated in the past with the toughest of its enemies, and now it is conducting, justifiably, negotiations with Hamas for the return home of (seized soldier) Gilad Shalit," the advertisment said.

"These negotiations must include an attempt to reach a comprehensive ceasefire with no pre-conditions," it said.

Shalit, an Israeli soldier, was seized by Palestinian militants who tunnelled into Israel from the Gaza Strip in June 2006. Egypt has been serving as a mediator in efforts to gain his release in return for Palestinians held in Israeli jails.

In their appeal, the signatories said a ceasefire would provide security for Israelis living near the Gaza Strip and prevent further suffering among Palestinians in the territory, which Israel often raids in a bid to curb rocket launchings.

The two authors are widely read in Israel and have long been vocal voices against Israeli occupation in the West Bank and Jewish settlement in the territory, but their appeal seemed unlikely to win wide support in Israel.

Oz, author of novels such as "My Michael" and "Touch the Water, Touch the Wind", is a founder of Israel's left-wing Peace Now Movement.

Grossman, whose novels include "The Smile of the Lamb" and "See Under: LOVE", is also a prominent peace activist. His son, a member of an Israeli tank unit, was killed in last year's Lebanon war.

The advertisment was published three days after Israel Radio reported that Israel rejected an approach from Hamas leader Ismail Haniyeh, through a "mediator", to a senior Israeli defence official.

A Palestinian official familiar with the situation said Hamas had sought talks with Deputy Defence Minister Matan Vilnai, offering to rein in rocket fire into Israel in return for an easing of Israeli border controls.

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