Less than six months after he was sworn into office, Barack Obama will make his maiden visit to the Arab world to add his name to a distinguished list of US Presidents who have tried, and largely failed, in their attempts to bring peace to the region.

At a speech in Cairo next month, Mr Obama will set out his plan to end the Arab-Israeli conflict, bury the painful legacy of the Bush Administration and set the US on a new course with the Islamic world.

If these lofty aims sound too good to be true, that is because they are. If America’s military limits were set out starkly during the Bush years, then its diplomatic reach is about to be exposed under Mr Obama’s leadership.

Arrayed against him are powerful forces with a vested interest in instability in the region, where mistrust of America is at a record high and where American forces are still involved in daily combat operations, from Iraq to Pakistan and Afghanistan.

The greatest challenge to any serious US peace effort is likely to be led by Iran, where President Ahmadinejad is favourite to be re-elected next month to another four-year term.

The Iranian regime has already dismissed Mr Obama’s gesture of conciliation and Mr Ahmadinejad stated that he plans to press ahead with the country’s nuclear programme. He will also continue to support militant groups such as Hamas and Hezbollah which are engaged in violent struggle with Israel. Any attempt to forge peace is likely to be met with force.

Israel, America’s main ally in the region, is the second largest obstacle. Under a right-wing Government, which does not recognise the rights of the Palestinians to statehood, Israel will use its considerable influence in Washington to resist any moves by the White House to “impose” a solution.

The last time an American President attempted this was George Bush senior, who took the Government and Yitzhak Shamir to task over Jewish settlements in the West Bank. The Americans ultimately forced the Israelis to sit down to peace talks in Madrid in 1991, but Mr Bush lost his re-election campaign, in part because he had alienated Jewish voters and the powerful Israel lobby.

The Madrid process, followed by the Oslo accords, the Camp David talks, the Road Map to peace and most recently the Annapolis peace conference all failed for a variety of reasons. There is plenty of blame to go around all the parties. That does not mean that Mr Obama should not try and that his mission is entirely doomed. There is a distinct possibility that Syria, Iran’s main ally in the Arab world, might yet be persuaded to come in from the cold, a move American diplomats are working hard to encourage.

Then there is Israel. The country’s right-wing coalition is fragile and came into being only after weeks of negotiations. If the climate in the region improves, it is possible that a more flexible government could come to power.

The best reason for trying is that the Middle East is unstable. Without some form of forward movement the region could slide backwards.

In the worst-case scenario, this could mean an Israeli attack on Iran’s nuclear facilities and large-scale retaliation by Tehran. Even a modest peace initiative has to be better than that.

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