BAGHDAD — The spiritual leader of Iraq’s Shiite majority called for a new, “effective” government Friday, increasing pressure on the country’s prime minister as an offensive by Sunni militants rages on.

Grand Ayatollah Ali al-Sistani’s comments at Friday prayers contained thinly veiled criticism that Shiite Prime Minister Nouri al-Maliki, in office since 2006, was to blame for the nation’s crisis over the blitz by the al-Qaida-inspired Islamic State of Iraq and the Levant.

While Al-Maliki’s State of Law bloc won the most seats in parliament in the Iraq’s April 30 election, he now faces opponents bolstered by criticism Thursday from U.S. President Barack Obama.

And with Iraq now asking the U.S. for airstrikes to temper the militants’ advance — especially as they apparently prepared Friday to again assault the country’s biggest oil refinery — al-Maliki appears increasingly vulnerable.

“It is necessary for the winning political blocs to start a dialogue that yields an effective government that enjoys broad national support, avoids past mistakes and opens new horizons toward a better future for all Iraqis,” al-Sisanti said in a message delivered by his representative Ahmed al-Safi in the holy city of Karbala.

The Iranian-born al-Sistani, who is believed to be 86, lives in the holy city of Najaf south of Baghdad.