The U.S. has failed to live up to its promises to help Iraq fight Islamic State extremists, unlike the “unconditional” assistance being given by Iran, the commander of Iraq’s powerful Shiite militias alleged Friday.

In a battlefield interview near Tikrit, where Iraqi forces are fighting to retake Saddam Hussein’s hometown from the militants of the so-called Islamic State, commander Hadi al-Amiri criticized those who “kiss the hands of the Americans and get nothing in return.”

Iraqi forces entered Tikrit for the first time Wednesday from the north and south. On Friday, they waged fierce battles to secure the northern neighborhood of Qadisiyya and lobbed mortar shells and rockets into the city center, still in the hands of Islamic State militants. Iraqi military officials have said they expect to reach central Tikrit in two to three days.

The Iranian-backed Shiite militias have played a crucial role in regaining territory from the Sunni extremists of the Islamic State group, supporting Iraq’s embattled military and police forces.

An Iraqi government official said Iran has sold Baghdad nearly $10 billion in arms and hardware, mostly weapons for urban warfare like assault rifles, heavy machine-guns and rocket launchers. The official spoke on condition of anonymity because he was not authorized to brief the media.

In November, President Barack Obama authorized the deployment of up to 1,500 more U.S. troops to bolster Iraqi forces, which could more than double the total of American forces in Iraq to 3,100. The Pentagon has made a spending request to Congress of $1.6 billion, focusing on training and arming Kurdish and Iraqi forces. According to a Pentagon document prepared in November, the U.S. is looking to provide an estimated $89.3 million in weapons and equipment to each of the nine Iraqi brigades.

The U.S.-led coalition of eight countries has launched more than 2,000 airstrikes in Iraq alone since August 2014, and the U.S. is also hitting the militant group from the air in Syria. Iraqi and U.S. officials have acknowledged the role airstrikes have played in rolling back the militants, saying the air campaign was an essential component in victories at the Mosul Dam, in Amirli, and more recently, in the crucial oil refining town of Beiji.

But the U.S. is not taking part in the operation in Tikrit, with U.S. officials saying they were not asked by Iraq to participate.

Al-Amiri, the Shiite militia commander who also is head of the Badr Organization political party, said that “help from Iran is unconditional.”

He warned that Iraq should not sacrifice its sovereignty for the sake of receiving weapons and assistance from the U.S., suggesting the Iraqi government is taking instructions from Washington.

“Our sovereignty is more important than U.S. weapons,” he said. “We can bring weapons from any country in the world.”

Separately, Grand Ayatollah Ali al-Sistani, Iraq’s top Shiite cleric, urged the government to step up its support for the Shiite militias and to take care of the families of militiamen killed in battle. His remarks were relayed by his spokesman Ahmed al-Safi in the Shiite holy city of Karbala.

As many as 30,000 men are fighting the extremists in Tikrit — most of them volunteers with various Shiite militias, Iraqi officials say. U.S. Gen. Martin Dempsey said Wednesday that up to 20,000 militiamen may be involved.

Karim al-Nouri, a spokesman for the Popular Mobilization Forces, the official name of the Shiite militias, said as many as 40 Iranian advisers are also taking part.