Sunni militants have blitzed through the vast desert of western Iraq, capturing four towns and three border crossings and deepening the predicament of the Shiite-led government in Baghdad led by Nouri al-Maliki.

The latest military victories — including two border posts captured Sunday, one along the frontier with Jordan and the other with Syria — considerably expanded territory under the militants' control just two weeks after the al-Qaida breakaway group began swallowing up chunks of northern Iraq, heightening pressure on al-Maliki to step aside.

The lightening offensive by the Islamic State of Iraq and the Levant takes the group closer to its dream of carving out an Islamic state straddling both Syria and Iraq. Moreover, controlling the borders with Syria will help it supply fellow fighters there with weaponry looted from Iraqi warehouses, significantly reinforcing its ability to battle beleaguered Syrian government forces.

If the Sunni insurgents succeed in their quest to secure an enclave, they could further unsettle the already volatile Middle East and serve as a magnet for Jihadists from around the world — much like al-Qaida attracted extremists in Taliban-ruled Afghanistan.

President Barack Obama, in an interview with CBS' "Face the Nation" aired Sunday, warned that the Islamic State could grow in power and destabilize the region. Washington, he said, must remain "vigilant" but would not "play whack-a-mole and send U.S. troops ... wherever these organizations pop up."

U.S. Secretary of State John Kerry, in the Jordanian capital on Sunday, also weighed in. The Islamic State, he warned, is a "threat not only to Iraq, but to the entire region."

The U.S. is looking for ways to work with Middle Eastern nations, most of them led by Sunni governments, to curb the Sunni militant group's growth. Officials in the United States and the Middle East have suggested privately that al-Maliki must leave office before Iraq's Sunnis will believe that their complaints of marginalization by the Shiite-led government in Baghdad will be addressed.

Al-Maliki, in office since 2006, has shown no sign he is willing to step down. However, he has been uncharacteristically silent since Obama and Iraq's top Shiite cleric both urged the prime minister last week to form an inclusive government that promotes the interests of all of Iraq's ethnic and religious groups.

Iraq's newly elected parliament must meet by June 30, when it will elect a speaker and a new president, who, in turn, will ask the leader who enjoys the support of a simple majority in the 328-seat chamber to form a new government. Al-Maliki's State of the Law won 92 seats, more than any other group but not enough to form a government.

The militants' stunning battlefield successes in the north and the west of Iraq have laid bare the inadequacies of the country's U.S.-trained forces and their inability to defend the rapidly shrinking territory they hold. In the north, troops fled in the face of the advancing militants, abandoning their weapons, vehicles and other equipment. In some cases in the west, they pulled out either when the militants approached or when they heard of other towns falling.