BAGHDAD/ WASHINGTON - 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. And in a sign the broad alliance of jihadists and anti-government elements behind the assault might be fracturing, internecine clashes killed 17 fighters in northern Iraq.Iraqi security forces on Saturday announced they were holding their own in several areas north of Baghdad, but officials said insurgents led by ISIL seized one of three official border crossings with Syria. 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.The takeover of Al-Qaim leaves just one of three official border crossings with Syria in the hands of the central government. The third is controlled by Kurdish forces. Insurgents led by the jihadist Islamic State of Iraq and the Levant (ISIL) already hold parts of the western province of Anbar, which abuts the Syrian border, after taking 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. Internecine clashes Obama’s refusal so far to agree to Iraq’s appeal for air strikes on the ISIL-led militants has prompted Baghdad’s powerful Shiite neighbour Iran to claim Washington lacks the will to fight terror. Meanwhile, Washington says Iran has sent a ‘small number’ of operatives into its neighbour. Obama told CNN on Friday: ‘There’s no amount of American fire power that’s going to be able to hold the country together.’The president, 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.’ Moreover, US President Barack Obama warned Friday that no amount of US firepower could keep Iraq together if its political leaders did not disdain sectarianism and work to unite the country.Obama told CNN, a day after announcing the dispatch of 300 special forces advisors to Iraq following a lightning advance by extreme Sunni radicals, that American sacrifices had given Iraq a chance at a stable democracy, but it had been squandered. ‘There’s no amount of American firepower that’s going to be able to hold the country together,’ Obama said in an interview. ‘I made that very clear to (Iraqi Prime Minister Nuri al-)Maliki and all of the other leadership inside of Iraq.’ Washington readied a new diplomatic push to unite Iraq’s fractious leaders Saturday and repel a Sunni insurgent offensive that has put Prime Minister Nuri al-Maliki under growing pressure domestically and overseas.US President Barack Obama has offered hundreds of military advisers but his refusal so far to approve air strikes against militants, led by the jihadist Islamic State of Iraq and the Levant, has prompted Baghdad’s powerful Shiite neighbour Iran to charge that Washington lacked the ‘will’ to fight terror.Sunni militants who fought together to capture swathes of Iraqi territory have turned their weapons on each other during clashes in Kirkuk province that cost 17 lives, sources said Saturday. The fighting erupted on Friday evening between the jihadist Islamic State of Iraq and the Levant (ISIL) and the Army of the Men of the Naqshbandiyah Order (JRTN) in Hawija, in Kirkuk province, said the sources.There were differing accounts as to what sparked the firefight, which is a potential sign of the fraying of the Sunni insurgent alliance that has overrun vast stretches of territory north of Baghdad in less than two weeks. One security official said JRTN fighters had refused an ISIL demand to give up their weapons and pledge allegiance to the jihadist force.