Iraq’s Ambassador Faleh al-Fayad is in Damascus today to discuss the possibility of a broad direct military cooperation with the Syrian government in their ongoing war against ISIS. Fayad has been meeting with Syrian President Bashar al-Assad.
There have been proposals for direct cooperation in the past, mostly initiated by Russia, though they have usually fallen apart pretty early in the face of US opposition. The US continues to seek regime change in Syria, which makes their position on ISIS in Iraq and ISIS in Syria a bit different.
It may be more likely now, however, with Iraq running out of specific ISIS-held territory within to contest, and having already shown interest in attacking ISIS targets across eastern Syria. Iraq has launched airstrikes against ISIS inside Syria in the past.
Iraqi Shi’ite militias have already been heading into Syria to fight ISIS there, and a lot of those militias are nominally under the charge of the Iraqi government. While Iraq and Syria are not close allies, the fact that both governments are Shi’ite dominated connects them, particularly in this increasingly sectarian war.