Shiite fighters paraded in Baghdad Saturday in a dramatic show of force aimed at Sunni militants who seized a Syrian border crossing, widening a western front in an offensive threatening to rip Iraq apart.

Meanwhile, Washington readied a new diplomatic bid to unite Iraq’s fractious leaders and repel insurgents whose lightning offensive has displaced hundreds of thousands, alarmed the world and put Prime Minister Nuri al-Maliki under growing pressure domestically and overseas.

In a sign that the broad alliance of jihadists and anti-government elements behind the offensive might be fracturing, internecine clashes killed 17 fighters in northern Iraq.

In Baghdad, thousands of fighters loyal to powerful Shiite cleric Moqtada al-Sadr paraded with weapons in the Sadr City district, vowing to fight the offensive which was launched on June 9.

Rank upon rank of fighters, dressed mostly in camouflage but some wearing black, bore Kalashnikov assault rifles, shotguns, sniper rifles, light machineguns and rocket launchers.

Some of the unit leaders carried Iraqi flags, while others held signs with messages including “We sacrifice for you, O Iraq,” “No, no to terrorism,” and “No, no to America”.

Fighters interviewed by AFP emphasized that they were not against any specific religious sect, and that their aim was to defend the country.

Similar parades were held in large southern cities including Basra, Najaf and Kut, all in the Shiite heartland.

Iraqi security forces announced they were holding their own in several areas north of Baghdad, but officials said insurgents led by ISIL seized control of one of three official border crossings with Syria.

Cross-border mobility

Militants took control of the area a day after 34 members of the security forces were killed in the border town, giving the fighters greater cross-border mobility into conflict-hit Syria.

Militants led by the jihadist Islamic State of Iraq and the Levant (ISIL) already control parts of the western province of Anbar, which abuts the Syrian border, after overrunning all of one city and parts of another earlier in the year.

It is unclear what impact the latest move will have on the overall offensive, as militants already have free reign along most of the 600-kilometre (375-mile) border, neither side of which is controlled by government forces.

ISIL aims to create an Islamic state that will incorporate both Iraq and Syria, where the group has become a major force in the rebellion against President Bashar Assad.

And 17 fighters were killed in clashes Friday evening between ISIL and the Army of the Men of the Naqshbandiyah Order (JRTN), another Sunni insurgent group, in militant-held territory in northern Kirkuk province.

The Sunni insurgents driving the recent offensive include a host of other groups, such as loyalists of now-executed dictator Saddam Hussein, and have formed a wide alliance.

Analysts say it is unclear if that grouping can hold together given disparate ideologies.

The parades in Baghdad and clashes elsewhere came as US President Barack Obama dispatched Secretary of State John Kerry to Europe and the Middle East in a new push for unity among Iraq’s fractious political leadership.

While Kerry is expected to travel to Iraq itself, it is not known exactly when he will do so.

Obama’s refusal so far to accede to Iraq’s appeal for air strikes on the ISIL-led militants has prompted Baghdad’s powerful Shiite neighbor Iran to claim Washington lacks the will to fight terror.

Meanwhile, Washington says Iran has sent a “small number” of operatives into its neighbor.

Obama told CNN on Friday: “We gave Iraq the chance to have an inclusive democracy, to work across sectarian lines, to provide a better future for their children.

“Unfortunately what we’ve seen is a breakdown of trust.”

“There’s no amount of American fire power that’s going to be able to hold the country together.”

Obama, who based his political career on ending the costly eight-year US intervention in Iraq, has insisted that Washington is not slipping back into the morass, but has offered up to 300 advisers and left open the possibility of “targeted and precise military action.”

Washington already has an aircraft carrier in the Gulf and is flying manned and unmanned surveillance flights over Iraq, while senior US officials say special forces being sent to advise Iraq could call in air strikes if necessary.

The US’s push for broader leadership came as Grand Ayatollah Ali al-Sistani, a revered cleric among Iraq’s Shiite Muslim majority, called on people to band together against the insurgents before it was too late.

UN aid agencies said they were rushing supplies to Iraq to help more than one million people displaced by the latest violence and unrest earlier this year.