Smoke rising from the Syrian border town of Kobani (Ayn al-Arab) following the US-led coalition airstrikes against the Islamic State targets near the Turkish-Syrian border crossing on October 28, 2014

When the United States and China discuss cooperating against Islamic State later this month, the most prominent outcome is likely to be less criticism of each other's anti-terrorism policies.

Both countries have flagged that President Barack Obama and President Xi Jinping will discuss the issue when they meet on the sidelines of the Asia Pacific Economic Cooperation (APEC) summit in Beijing.

Cooperation like sharing intelligence will be difficult. And China will not commit troops or weapons.

But simply seeing eye-to-eye on the problem of Islamic State can pay political dividends, experts and diplomats say, as the United States launches air strikes against the ultra-radicals in Iraq and Syria and China faces condemnation of its hardline tactics in its western Xinjiang region.

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"You're mostly likely to see China sit back and not criticise the United States. That is what cooperation looks like," said Philip Potter, an assistant professor at the University of Virginia who studies global terrorism.

In return, Beijing would value more recognition from Washington of what Chinese authorities say is the threat of militant Islamic separatists in its far western province of Xinjiang.

China charges that a group called the East Turkistan Islamic Movement (ETIM) is seeking to set up a separate state in Xinjiang, home to the Muslim Uighur ethnic minority.

Rights groups and Uighur exiles dispute the extent of the ETIM threat, and argue that economic marginalization of Uighurs is one of the main causes of violence there.