Giuliani has long been a critic of the idea of a Palestinian state

In an essay, he said it was not in the US interest to help create a state that, he said, would support terrorism.

He also said he would consider talks with Iran, so long as its rulers understood the US might be prepared to destroy Iran's nuclear infrastructure.

The former New York mayor leads polls for the Republican party's nomination.

Outlining his foreign policy views in the latest issue of Foreign Affairs magazine, Mr Giuliani said too much emphasis had been placed on brokering negotiations between Israel and the Palestinians

Palestinian statehood will have to be earned through sustained good governance, a clear commitment to fighting terrorism, and a willingness to live in peace with Israel

Rudy Giuliani

"It is not in the interest of the United States, at a time when it is being threatened by Islamist terrorists, to assist the creation of another state that will support terrorism," he wrote.

"Palestinian statehood will have to be earned through sustained good governance, a clear commitment to fighting terrorism, and a willingness to live in peace with Israel.

"America's commitment to Israel's security is a permanent feature of our foreign policy."

President George W Bush is in favour of a Palestinian state and has been seeking to bolster the position of Palestinian Authority President and Fatah leader Mahmoud Abbas.

'Position of strength'

Mr Giuliani has been a consistent critic of the idea of a Palestinian state and of Palestinian leaders.

In 1995, as New York's mayor, he banned the late Palestinian leader Yasser Arafat from city-sponsored events related to the United Nations' 50th anniversary celebrations.

Mr Giuliani said the US might enter negotiations with Iran from a "position of strength".

"The theocrats ruling Iran need to understand that we can wield the stick as well as the carrot, by undermining popular support for their regime, damaging the Iranian economy, weakening Iran's military, and, should all else fail, destroying its nuclear infrastructure," he said.