U.S. Secretary of State John Kerry was in Baghdad on Wednesday, beginning a tour of the Middle East to build military, political and financial support to defeat Islamic State militants controlling parts of Iraq and Syria.

Kerry said he was impressed by Prime Minister Haider al-Abadi's plans to rebuild the Iraqi military and push broad political reforms.

Abadi formed a new, more inclusive, Iraqi government on Monday in a move Washington said was vital before there could be further U.S. action to help push back the militants who took over large parts of northern Iraq this year.

Kerry told Abadi he was "encouraged" by his plans for "reconstituting" the military and "your commitment to broad reforms that are necessary in Iraq to bring every segment of Iraqi society to the table."

Abadi appealed to the international community to help Iraq fight Islamic State, urging them "to act immediately to stop the spread of this cancer".

"Of course our role is to defend our country, but the international community is responsible for protecting Iraq and protecting Iraqis and the whole region," Abadi said.

Kerry's tour will include Saudi Arabia and probably other Arab capitals.

Last week nine countries, most of them in Europe, were named as the core group of a coalition U.S. President Barack Obama says will degrade and destroy Islamic State, which has declared a caliphate in land it took over and executed many prisoners, including two American journalists who were beheaded.  

Two days after Iraq formed a new government, Kerry arrived in Baghdad to "take it to the next level", as a senior U.S. official put it, and find a way to defeat Islamic State.

Abadi faces multiple crises from the need to pull Sunni Muslims back from armed revolt to persuading minority Kurds not to break away and convincing Abadi's own majority Shi'ites he can protect them from Sunni hardliners.

Kerry highlighted Abadi's readiness "to move forward rapidly on the oil agreements necessary for the Kurds, (and) on the representation of Sunnis in government and participation."

His visit comes hours before a speech in which Obama will try to rally Americans behind another war in a region he has long sought to leave, backed by what Washington hopes will be a coalition of NATO and Gulf Arab allies committed to a campaign that could stretch beyond the end of Obama's term in 2016.

"We're now at the stage of beginning to build a broad-based coalition," a senior U.S. State Department official said. "There is, of course, military support, and that's everything from logistics and intelligence and airlifts and all the things it takes to conduct an effective military campaign."

ENTRENCHED SECTARIAN TENSIONS

Unlike his predecessor, Abadi enjoys the support of nearly all of Iraq's major political groups, and the two most influential outside powers, Iran and the United States. U.S. officials hope he will present a unified front to weaken Islamic State, which has seized a third of both Iraq and Syria.

But it will be hard to placate all the forces in Iraq. On Wednesday, cleric Moqtada al-Sadr, head of a powerful Shi'ite movement, said Iraq should not cooperate with "occupiers", a reference to the United States. Sadr's opinions hold sway over tens of thousands of militants.

Three car bombs exploded on Wednesday in a Shi'ite neighborhood in eastern Baghdad, killing nine people and wounding 29, a police officer said.

While it is unclear what steps will be taken to strengthen the Iraqi army after its collapse in the face of an Islamic State onslaught in June, the senior U.S. official said tentative plans for a new National Guard unit, announced by Abadi on Monday, were intended to deprive Islamic State of safe havens by handing over security to the provinces.

The new Iraqi National Guard, the U.S. official suggested, was an evolution from the Awakening movement of Iraqi tribes and urban units that helped U.S. forces repel al Qaeda in 2007-10.

But while the United States hailed the new government as a breakthrough, sectarian tensions appeared as entrenched as ever, possibly worsened by a month of U.S. air strikes on Sunni jihadists.

While Kurdish and Shi'ite fighters have regained ground, Sunni Muslims who fled the violence near the northern town of Amerli are being prevented from returning home and some have had their houses pillaged and torched. Sunni Arabs are also feeling a backlash in villages where they used to live alongside Kurds, who accuse them of collaborating with Islamic State.

On Wednesday, Shi'ite militia north of Baghdad forced dozens of Sunni families from their homes during an offensive, stole possessions and burned their houses, a Shi'ite policeman and government source in the area told Reuters, asking for anonymity to allow them to report on the offensive, which they said they opposed.

The fallout risks worsening grievances that helped Islamic State find support amongst Iraq's Sunnis and may make it more difficult to convince them to fight the militants, who portray the U.S. strikes as targeting their minority sect.

While the U.S. official praised weeks of U.S. air strikes as "highly precise" and "strategically effective", he acknowledged much work lay ahead. "It's going to be a very difficult, long road to get there," he said.

Any campaign to defeat Islamic State could take one to three years, Kerry said.

Kerry will meet Jordan's King Abdullah later on Wednesday, and travel on Thursday to Saudi Arabia for talks that will include Egypt, Turkey, Jordan and the six-country Gulf Cooperation Council (GCC), which comprises Saudi Arabia, Bahrain, the United Arab Emirates, Kuwait, Oman and Qatar.

Saudi Arabia is unnerved by the rapid advance of Islamic State and fears it could radicalize some of its own citizens and lead to attacks on the U.S.-allied government. Arab League foreign ministers agreed on Sunday to take all necessary measures to confront Islamic State.

Obama wants Gulf Arab states to crack down on the flow of money and foreign fighters to Islamic State, consider military action and support to Sunni Muslim moderates in Iraq and Syria, possibly through direct funds.

In Jordan, Kerry is expected to receive requests for extra military aid, including helicopters and border security equipment, along with part of the $500 million the Obama administration has proposed to accelerate training of moderate Syrian rebels, a Jordanian official told Reuters.

Jordan is considered a top choice to host the training of the rebels due to its close security relationship with Washington, proximity to neighboring Syria and pool of more than 600,000 Syrian refugees. Jordan, however, fears retaliation from Syria if its territory is used for overt training.

French President Francois Hollande will travel to Baghdad on Friday to meet Iraqi authorities ahead of a conference of regional and international powers in Paris on Monday to coordinate efforts to tackle Islamic State. It will be attended by Iraq's new president, Fouad Massoum.

"Any action must be coordinated and targeted," a senior French diplomat said. "We have to keep our autonomy as we aren't the United States' subcontractor."

The diplomat said action in Iraq needed to be tied with progress in Syria: "We need to think of ways to attack Daesh (IS), which may also weaken (Syrian President Bashar) al-Assad."

(Additional reporting by Oliver Holmes in Baghdad, Isabel Coles in Arbil, Suleiman Al-Khalidi in Amman, John Irish in Paris and Angus McDowall in Riyadh; Editing by Janet Lawrence)