WASHINGTON — One month after Iraq’s prime minister assured American officials here that his Shiite-dominated government was striving to build a multisectarian state, two leading Sunni politicians said Monday that Sunnis were being squeezed out of the country’s political system.

“Are we part of Iraq?” Rafe al-Essawi, a former deputy prime minister and one of the leading Sunni figures in Iraq, said in an address at the Brookings Institution. Sunnis are looking to see “if there is any benefit in political participation.”

Appearing at the same event, Atheel al-Nujaifi, the governor of the embattled Nineveh Province, complained that the Iraqi government had yet to provide weapons to thousands of Sunni fighters eager to join an eventual military operation to retake Mosul, the provincial capital, from the Islamic State militant group.

So wary are the Sunnis of the authorities in Baghdad that Mr. Nujaifi urged that Nineveh Province be granted autonomy if Islamic State fighters were evicted, though as part of an Iraqi federal system.