Washington: Anyone who wants to understand why Israel has such unwavering support from the United States should speak to one man.

Fiery television evangelist Pastor John Hagee has emerged as the rallying voice for thousands of American Christians, who believe Israel is doing God's work in a "war of good versus evil".

When he strode on to a stage in Washington last month, he was cheered to the rafters by 3,500 evangelicals as well as by Israel's ambassador to America, a former Israeli chief of staff and a host of US congressmen of both parties.

"After 25 years of hammering away at the truth on national television, millions of people have come to see the truth of the word of God," Hagee told The Daily Telegraph. "There is literally a groundswell of support for Israel in the US among evangelicals."

Twenty-five years ago, Hagee was denounced as a heretic when he urged his fellow preachers to speak out in support of Israel. He also met with suspicion from Jews who thought that anti-Semitism was the standard evangelical belief. When he persevered and hosted a night to honour Israel in his hometown, San Antonio, there was a bomb threat and panicked followers ran for the door.

But today most of America's 60 million Christian evangelicals, who make up about a quarter of the US electorate and the essence of the President's "base", are behind Bush's pro-Israeli position and are pushing for a showdown with Iran. As many as half of those are Christian Zionists.

Hagee said: "What we have done is united all of this evangelical horsepower and said, 'We're not just going to Washington to stand on the grass and sing Amazing Grace. We're going into the halls of Congress to see the senators and to see the congressmen face-to-face, and to speak to them about our concerns for Israel'."

His claim of political clout is no idle boast. The President sent a message of support praising him for "spreading the hope of God's Love and the universal gift of freedom". They met several times when Bush was governor of Texas.

America has long identified with Israel. This backing has been shored up in Washington by the influential Israeli lobby. It also reflects a cultural affinity which is greater in the wake of the 9/11 attacks: for most Americans, Israel is on the front line against terrorism.

Another key factor is Christian Zionism: a movement based on the idea that Israel's travails fulfil Biblical prophecy and are a forerunner of the battle of Armageddon and the Second Coming.

Outside Hagee's mega-church is a facsimile Wailing Wall. Inside on a flagpole is the Israeli flag and tributes from Israeli visitors, including prime minister Ehud Olmert, who visited several times when he was mayor of Jerusalem.

The Telegraph Group Limited, London 2006