Kerry in Baghdad

US Secretary of State John Kerry arrived in Baghdad on Monday, where he is expected to push Iraq's Shiite Prime Minister Nouri al-Maliki to form a more inclusive government, as Sunni Islamist militants threaten to partition the country.

State Department spokeswoman Jen Psaki said that Kerry and Maliki will discuss actions the US is taking to assist Baghdad in its fight against the Islamic State in Iraq and Syria (ISIS).

The secretary of state will also "urge Iraqi leaders to move forward as quickly as possible with its government formation process to form a government that represents the interests of Iraqis."

Iraq's Sunnis have long complained that they are the victims of systematic discrimination at the hands of the country's Shiite-led central government.

ISIS made rapid advances over the weekend, pushing deep into Anbar province, Iraq's Sunni Muslim heartland. ISIS has captured the towns of Qaim, Rawah, Anah and Rutba since Friday.

The fall of Rutba, which lies on the main highway connecting Iraq and Jordan, has effectively cut Baghdad off from its western neighbor.

Jordan reinforces frontier

Meanwhile, Sunni tribes in Iraq have seized the Turaibil border crossing with Jordan after government forces abandoned their posts, according to security sources from both countries. Turaibil is the only legal crossing between Iraq and Jordan.

The tribesmen were reportedly negotiating a handover of Turaibil to ISIS militants, who have also seized two key border crossings with Syria.

The Turaibil border crossing has been effectively closed, according to two unnamed Jordanian officials quoted by the Reuters news agency on Sunday.

Amman has fully deployed its military along Jordan's 181-kilometer (112-mile) border with Iraq, in response to the rapid advances made by ISIS.

Risk of spillover

In an interview on CBS television's Face the Nation on Sunday, US President Barack Obama warned that instability in Iraq could spill over into neighboring Jordan.

"We're going to have to be vigilant generally," he said. "Right now the problem with ISIS is the fact that they're destabilizing the country [Iraq]."

"That could spill over into some of our allies like Jordan," Obama added. "They (ISIS) are engaged in wars in Syria where - in that vacuum that's been created - they could amass more arms, more resources."

But according to Marwan Muasher, a former Jordanian foreign minister, Amman's security forces are capable of keeping ISIS militants at bay.

"We have a very strong army and intelligence service, so you cannot equate the threat that they posed to a state like Syria or even Iraq to the one that they might pose to Jordan," Muasher, vice president of the Carnegie Endowment, told the Associated Press.

slk/kms (AP, AFP, Reuters)