WASHINGTON  - Secretary of State John Kerry signalled on Monday that the United States would be open to cooperating with Iran militarily in Iraq to beat back militants who pose an ‘existential’ danger to that war-torn country.

‘This is a challenge to the stability of the region. It is obviously an existential challenge to Iraq itself. This is a terrorist group,’ Kerry told Yahoo News on the sidelines of a State Department conference on saving the world’s oceans.

Kerry said that drone strikes were an option in combating the offensive, after US President Barack Obama said he was weighing ‘all options’ on how to support the Iraqi government.

Drones might not be the ‘whole answer,’ Washington’s top diplomat told Yahoo News, ‘but they may well be one of the options that are important to be able to stem the tide and stop the movement of people who are moving around in open convoys and trucks and terrorising people.’

Prodded on whether the United States would consider cooperating militarily with Iran, Kerry replied: ‘Let’s see what Iran might or might not be willing to do before we start making any pronouncements.’

As the top US diplomat, Kerry has played a central role in what may be the Obama administration’s biggest foreign policy gamble: negotiations with Iran over its suspect nuclear program. Those talks resume this week, with time running short to reach a deal that would lift crippling economic sanctions in return for steps designed to prevent Tehran from developing nuclear weapons.

 AFP adds: Militants battled security forces for control of a strategic town in north Iraq Monday, forcing half the area’s population to flee. Militants from the Islamic State of Iraq and the Levant (ISIL) militant group are said to have killed scores of Iraqi soldiers as they pushed an advance on the capital, including in a ‘horrifying’ massacre that has drawn international condemnation. In the latest fighting on Monday, militants entered and took control of several neighbourhoods of Tal Afar, a Shia Turkman-majority town in Nineveh province, according to officials and residents.

A White House official said on Monday that there could be talks with Iran on the sidelines of meetings on Tehran’s nuclear program about the mounting crisis in Iraq, but the United States is not interested in any military coordination with Tehran. ‘Any of those conversations that may occur on the margins are entirely separate from the conversations about Iran’s nuclear program,’ White House spokesman Josh Earnest told reporters traveling with President Barack Obama. ‘Any conversations with the Iranian regime will not include military coordination,’ Earnest said. ‘We’re not interested in any effort to coordinate military activities with Iran.’