BAGHDAD — Embattled Prime Minister Nouri al-Maliki rejected demands Wednesday from rival politicians for an emergency national unity government, as Al Qaeda-inspired insurgents gained more ground, assaulting a former US air base and pushing toward one of the country’s largest dams.
In his weekly address to the nation, he described such efforts as a ‘‘rebellion’’ against the constitution. The United States is pressuring Iraq to create a more inclusive government, urging Maliki, a Shi’ite, to reach out to the country’s disaffected Sunni Muslim minority.
With the country’s conflict expanding, Baghdad is locked in a period of intense political maneuvering that could result in Maliki’s loss of the premiership. Given the violence, he is likely to struggle to form a government although his party won the largest share of the vote in April parliamentary elections, analysts said.
Despite his outright rejection of a ‘‘national salvation’’ government demanded by politicians, including the secular Shi’ite Ayad Allawi, he struck a somewhat conciliatory tone in his speech.
He urged political parties to lay aside their differences before the first session of Iraq’s newly elected Parliament, expected to take place next week.
‘‘We desperately need a united national stance to defy terrorism,’’ said Maliki.
His speech, delivered two days after he met with Secretary of State John F. Kerry, contrasted sharply with his public declarations earlier in the crisis, which have appealed to religious motivations and called for citizens to protect the country’s Shi’ite Muslim shrines.
Maliki issued the appeal as Sunni Muslim militants attacked one of Iraq’s largest air bases and seized several small oil fields north of the capital, news agencies reported.
In addition, insurgents were advancing on the Haditha Dam and hydroelectric power plant on the Euphrates River about 175 miles northwest of Baghdad.
There were also reports that Iran is stepping up its intervention on behalf of Maliki, secretly supplying military equipment and using drones to conduct aerial surveillance.
In Brussels, where he attended NATO meetings Wednesday, Kerry said the conflict in Iraq has ‘‘been widened obviously in the last days with reports of [Iranian Revolutionary Guard] personnel, some people from Iran being engaged in Iraq, perhaps even some Syrian activities therein.’’
Kerry told reporters, ‘‘That’s one of the reasons why government formation is so urgent, so that the leaders of Iraq can begin to make the decisions necessary to protect Iraq without outside forces moving to fill a vacuum.’’
He said he briefed other NATO foreign ministers about his meetings with Iraqi leaders earlier this week in Baghdad and Irbil.
Striking a positive note, Kerry also said he was not sure what Maliki meant in rejecting a ‘‘salvation government’’ but that the rest of Maliki’s address was in line with what he pledged to do in their meeting.
Syrian government aircraft bombed Sunni militant targets inside Iraq on Tuesday, further broadening the crisis that is threatening to engulf the entire Middle East.
Israeli warplanes and rockets struck targets inside Syria.
Iraqi news media reported that at least 20 people were killed and 93 injured in the strike by Syrian jets on an Iraqi border town controlled by the Islamic State of Iraq and Syria.
Western officials who confirmed the attack said they had no casualty details on the strike, which targeted a market in the town of Qaim, according to the nongovernment National Iraqi News Agency.
CNN reported Wednesday that at least 57 Iraqi civilians were killed and more than 120 others injured in Syrian airstrikes on several border areas of Anbar province Tuesday, including Rutba, Walid, and Qaim.