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TEL AVIV, Dec 12 (Reuters) - Israel's army chief said on Wednesday daily strikes against Palestinian militants in the Gaza Strip were having an impact but he believed a big military offensive would be needed.

Speaking at a conference in Tel Aviv on security issues, Lieutenant General Gabi Ashkenazi said that daily Israeli incursions into the coastal territory were hurting militants but could not be decisive in curbing attacks against Israel.

"We are operating in Gaza on a daily basis. Yesterday we returned from a broad operation ... this brings a reduction in the ground threat and the firing of rockets but does not stop it," Ashkenazi said. "We will come to the point where we will have to carry out the big operation."

The military on Wednesday presented Prime Minister Ehud Olmert's security cabinet with plans to keep up small incursions into Gaza but said a broader invasion was not imminent, an official who attended the meeting said.

Ashkenazi was speaking a day after Israel mounted one of its biggest raids into the Hamas-run Gaza Strip since the Islamist group seized control in June, killing five militants as dozens of tanks and armoured cars pushed into the territory.

Ashkenazi said he believed that there was "military value" in repeated strikes on militants but that they probably could not be completely effective in stopping attacks against Israel.

Hamas, which routed Palestinian President Mahmoud Abbas's Fatah faction in Gaza, has rejected a peace push with Israel and its grip on the territory could complicate talks.

Israel regularly launches raids into the Gaza Strip to try to stop militants firing rockets and mortars into Israel.

Ashkenazi was making a rare public appearance at a security conference organised by the Tel Aviv-based Institute for National Security Studies in which he laid out the Israeli military's long-term security plans. (Writing by Ori Lewis; Editing by Keith Weir)

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