Sunni insurgents in Iraq appeared to consolidate their gains in the west of the country over the weekend while government forces withdrew from the Jordanian border on Monday to concentrate on defending the capital, Baghdad.

After a surprise offensive two weeks ago in which they took control of Iraq’s second city, Mosul, militants from the Islamic State of Iraq and the Levant (ISIS) — a jihadist group that is also active in neighboring Syria — have focused on conquering territory and border towns they bypassed.

In the northwest, the group, which has been disavowed by the international terrorist organization Al Qaeda, took Tal Afar, situated between the Syrian border and Mosul.

Ruthba, a city close to the Jordanian border, was apparently abandoned by government forces, allowing militants to move in. Tribal fighters later took over the only legal crossing point between Iraq and Jordan.

For the insurgents, capturing the frontier is a dramatic step toward their goal of erasing the modern border altogether and erecting an Islamist state in the Sunni lands between the Euphrates and Tigris Rivers.

Before the capture of Mosul, militants already controlled the area around Fallujah and Ramadi in Anbar Province which was the hotbed of the Sunni insurgency against the Western occupation of Iraq between 2003 and 2011.

While popular support for ISIS — which advocates a purist interpretation of Islam and a strict adherence to Islamic law — seems limited, Sunni resentment in Iraq runs high. The sect accuses Prime Minister Nouri al-Maliki’s government of favoring Shia Muslims over Sunnis, fueling sympathy for the latest uprising.

Despite international calls for reforms to give Iraq’s Sunni minority a greater say in how they are governed, Maliki’s allies last week declared a boycott of the country’s biggest Sunni political bloc while the prime minister himself lashed out at Sunni monarchies in the Persian Gulf, accusing them of promoting “genocide” in the country by supporting militant groups that also battle the Shia regime of President Bashar Assad in Syria.

The Americans have conditioned military support for Maliki’s government on political changes, feeding suspicion that they seek the prime minister’s resignation.

On a visit to Baghdad on Monday, Secretary of State John Kerry emphasized that the United States wanted Iraqis to “find a leadership that was prepared to be inclusive and share power.”

President Barack Obama last week promised to send up to three hundred special forces troops as advisors to Iraq but has held off from providing airstrikes and ruled out redeploying ground troops.