ANKARA (AFP) ― Iran’s president begins a landmark trip to Turkey on Monday as the two countries try to build trade ties despite an often fraught competition for regional influence and deep differences over the Syrian war.

Iranian President Hassan Rouhani will meet his Turkish counterpart Abdullah Gul and Prime Minister Recep Tayyip Erdogan in Ankara, where the powerful neighbours are expected to discuss security concerns as well as trade opportunities.

The two sides have had a complex and often dysfunctional relationship, which has taken an especially bitter turn in recent years as a result of increasing competition between Sunni and Shia Muslim powers across the region.

This has become more pronounced following the onset of the Syrian civil war, in which the two have found themselves on opposite sides.

Iran, a Shia theocracy, is the chief backer of Syrian President Bashar al-Assad, while Sunni-majority Turkey has moved from trying to encourage reform in Syria to overtly supporting the armed opposition. The two also compete for influence in Iraq, Central Asia and the Caucasus.

Even on areas where they might be thought to cooperate ― such as Kurdish separatism ― they have often sought to undermine each other. Both Turkey and Iran face a threat from Kurdish rebels who wish to break away and form their own country.

But instead of cooperating, the two governments have sponsored rebels in the others’ backyard over the years.

In 2012, Turkish media reported government claims that more than 100 Iranian agents were active in Turkey, working on behalf of the Kurdistan Worker’s Party ― a Kurdish rebel group that fights for autonomy for Kurds.

“We have agreements as well as disagreements,” was the summation of the Iranian embassy spokesman in Ankara last week.