The US has begun airstrikes to support Iraqi government efforts to recapture the city of Tikrit from the Islamic State (IS) terrorist group, overcoming earlier resistance to its intervention, Efe news agency reported.

“At the request of the government of Iraq, coalition forces are providing support to Iraqi security forces as they combat ISIL (as IS was previously known) in and around Tikrit,” said Patrick Ryder, spokesperson for US Central Command responsible for operations in the Middle East.

“To be clear, the coalition is only coordinating with the government of Iraq and the Iraqi security forces; we do not coordinate our operations in any way with Iran or Iranian-backed militias,” Ryder said in a statement on Wednesday.

US support in Tikrit includes air raids, intelligence, and advice.

The airstrikes began cautiously on Wednesday, reflecting American concerns about the presence of Iranian military in the scenario, after operations to retake Tikrit came to a standstill last week.

According to the New York Times, both the Iraqi government and Shia militias had previously assured the US that its intervention was not necessary.

The announcement of support from the US-led coalition came as the Iraqi armed forces and local Sunni tribes fight together with Iranian-backed Shia militia for control of Tikrit.

The US has consistently denied coordinating with or providing support to Iranian-backed militias, and reiterated that military assistance is limited to the mostly Shia Iraqi army.

However, the offensive on Tikrit is led by about 20,000 Shia militiamen trained and armed by Iran and, according to local sources, under the command of Iranian General Qasem Suleimani, head of Al Quds Brigade.

The Shias, the Iraqi army and Sunni tribals have made advances in recent days but failed to regain control of the city.

Capturing Tikrit, a city located in the heart of the Sunni Iraq, is critical to advancing on Mosul, Iraq’s second largest city and under IS control since June 2014.