TEL AVIV (Reuters) - Amnon Lipkin-Shahak, Israel's top soldier until five months ago, formally retired from the army on Thursday and cleared the way to form a centrist party to challenge Prime Minister Benjamin Netanyahu.

In his first interview about his political plans, the former army chief told the newspaper Ha'aretz he wanted the number one or two position in a party he believed could oust Netanyahu.

The Knesset, Israel's parliament, voted on Monday to move elections scheduled for late 2000 to early 1999 after Likud party leader Netanyahu lost the support of right-wingers who felt he had betrayed them by agreeing to give up West Bank land in a peace deal with the Palestinians.

An election date has yet to be set. Opinion polls have shown Shahak to be a leading contender.

Shahak said in the interview he believed the left wing alone, headed by the left-center Labour party of Ehud Barak, could not win the elections.

A soldier for 36 years, Shahak was, like Barak, a protege of slain Prime Minister Yitzhak Rabin. While deputy army commander, Shahak was charged by Rabin with launching Israel's first peace talks with the Palestinians that emerged from the secretly negotiated Oslo deal. The deal remains the basis for Middle East peacemaking.

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