Condoleezza Rice will have no easy moments during her week on the road. The Middle East is in a profound and long-term crisis, and the United States is intimately involved.
By Jeremy Bowen
BBC Middle East Editor
The rise of Iraq's Shia Muslims alarms many Sunni Arab states
She will want to sell the new American plan to send more troops to Iraq to US allies in the Gulf. In Washington it has been condemned by Democrats and dissident Republicans as a dangerous escalation of the war.
Ms Rice might be hoping for a more receptive audience in the Gulf.
After all, the region's Sunni Muslim ruling families want to keep their strongest ally engaged in their part of the world.
But they might also want to ask Ms Rice whether the plan to send 20,000 more American troops to Iraq will make their problems worse, not better. After all, the most serious challenges they face were, to a large degree, made in America during the period in 2002 and 2003 when the White House and the Pentagon were planning for war in Iraq, but not thinking too hard about what would happen after they reached Baghdad.
Saudi Arabia and the Gulf states have bloodshed on their doorsteps, and that is not comfortable. Iraq has become a base for Sunni extremists who despise the Gulf rulers who are in the American camp.
The Shia factor
But even more serious for the Gulf's ruling families - and less directly the authoritarian Sunni regimes in Jordan and Egypt - is the growing empowerment of Shia Muslims. It is perhaps the single biggest unintentional consequence of George Bush's decision to invade Iraq and it will be making Sunnis nervous for at least a generation.
[President Bush] might even find more support for his approach to international relations in the Knesset in Jerusalem than in the Congress in Washington DC
The era of Sunni dominance is ending. Shias have been dominant in the Iraqi government ever since it was re-established by the Americans. By removing Saddam Hussein, the Sunni strongman, the Americans also obligingly removed Shia Iran's biggest local enemy.
The Shia minorities in Sunni-ruled Saudi Arabia, Kuwait and Bahrain all watched it happen with great interest. So did Shia Muslim Hezbollah in Lebanon, whose fighters gave Israel a bloody nose and a long-running political and strategic headache after last summer's war.
The indications are that the Americans are preparing themselves - and their allies - for a moment when they go after Iraq's strongest Shia militia, the Mehdi Army, which is led by the cleric Moqtada Sadr. That could ignite a wider Shia uprising in Iraq, and increase the restiveness among Shia minorities in the Gulf States. President Bush has also threatened to use his troops against what the US believes are infiltration routes into Iraq from Syria and Iran.
Condoleezza Rice denies that taking the war to Syria and Iran would be an escalation, which is how it will be seen by many critics of US policy. In an interview with the BBC, she said it was simply "good policy", a reaction to unacceptable and lethal Iranian activities against US forces. The US put a warning shot across Iran's bows a few days ago when its soldiers raided Iranian offices in the Kurdish town of Irbil in Northern Iraq.
During her visit, Secretary of State Rice will try to explain to Gulf rulers why she believes the rewards beat the risks. She told senators in Washington that the consequences of an American failure in Iraq were enormous, not just for the US and for Iraq, but also for the whole Middle East and the wider world.
That is one thing that people on all sides of the argument can probably agree on. Where they differ is on whether or not the failure is already happening. Condoleezza Rice has to persuade her hosts that it is not yet unavoidable.
Friends and foes
The other big part of the trip will be her latest visit to Israel and the Palestinians. The Americans do not pretend to have new ideas to bring the Israelis and the Palestinians closer together.
In Israel there is plenty of talk about the need to take military action against Iran at some point in the future, especially if the US will not
In her BBC interview, the secretary of state said she hoped to "move forward, perhaps even accelerate" the road map. That is the US-backed peace plan that was supposed to lead to the creation of a Palestinian state.
It has been moribund almost since it was tabled in 2003, partly because the Bush administration and Israel were lukewarm about it, and partly because neither Israel nor the Palestinians have fulfilled the obligations they have in it.
When President Bush came to power, the Americans were the only power with the clout to influence both sides. He chose not to use it.
He has been criticised for not putting America's weight behind a diplomatic offensive that would force the two sides to fix a price for peace. But since 9/11 President Bush has viewed the Israeli-Palestinian conflict, just like the rest of US foreign policy, through the prism of the war on terror.
That is not going to change. In his last two years in office, Iraq will take most of his administration's energies, and President Bush anyway appears to be happy with the American approach to the Palestinian-Israeli conflict.
His world is divided up into friends and enemies. He has rejected the advice of the Baker-Hamilton report on Iraq to start a diplomatic initiative to include Syria, Iran and to push towards ending the conflict between Israel and the Palestinians.
For the president, Israel is America's friend, closer than any other and more deserving of support. It is not conceivable that George Bush would ever consider putting the sort of pressure on Israel that would produce the kind of concessions that the Palestinians want even as the bare minimum for a deal - even if he could get the idea past his electorate.
Anyway, after the thumping President Bush's Republicans took at the mid-term elections late last year because of the Iraq war, he might even find more support for his approach to international relations in the Knesset in Jerusalem than in the Congress in Washington DC.
It is also inconceivable that the Palestinians will satisfy Israel's security needs. No Palestinian leader can unite the divided factions in a brutalised society that is crumbling under the weight of occupation and international financial sanctions.
The most significant American intervention there in the last few months has been the decision to permit the transfer of weapons to forces loyal to the generally conciliatory Palestinian President, Mahmoud Abbas, to bolster them against their Islamist rivals, Hamas.
When she visits Israel, Condoleezza Rice will certainly talk about how to reduce tensions in the occupied territories. But she will also be discussing Iran, and its nuclear plans.
The United States and Israel are at the forefront of the campaign to stop what they believe is Iran's plan to acquire nuclear weapons.
In Israel there is plenty of talk about the need to take military action against Iran at some point in the future, especially if the US will not.
Israel will also be reassured by the recent news that the CIA is going to start making moves in Lebanon against Hezbollah. The United States was disappointed that Israel was not able to deliver its stated objective in the war last summer of eliminating Hezbollah as a military force in Lebanon. It saw Israel's fight as its fight, a battle in the War on Terror, its proxy against Iran's.
Is Condoleezza Rice moving through a region where divisions are hardening into the shape of what might become the next war? In Iraq, there could be an axis between the US and Saudi Arabia, which seems to be indicating that it is prepared to intervene to help its Sunni brothers; against them would stand Iran and its Shia allies. A war like that would start renewed fighting between Israel and Hezbollah which would most likely pull in Syria.
That nightmare need not come to pass, Ms Rice might suggest, if the militant Palestinian factions listen to reason and the new US plan for Iraq works, if Iran does as it is told and stops meddling in Iraq and as long as Tehran responds to diplomatic pressure to end its nuclear programme.
Those are three big "ifs", in a world of danger.