Visit comes amid an economic downturn.
The accusation is likely to strain ties between Turkey and Iran, two regional powers which had grown closer under the government of Turkish President Tayyip Erdogan.
Assad and Zarif will discuss regional and international developments and avenues for preserving the peace in the region, according to MEHR.
Erdogan said Turkey will continue to buy natural gas from Iran in line with its long-term supply contract despite Trump's threats to punish countries doing business with Iran.
The problem is that the US has no clear plan now for Syria, while its adversaries appear to have one.
Iran is a key ally of the Syrian government in the seven-year civil war and it says it has no intention of withdrawing unless Syria requested it do so.
The US and Russia, two world super-powers, and Turkey and Iran, the two regional Islamic powers, are locked into a deadly confrontation with no political issue in sight.
President Tayyip Erdogan said last year Turkey would build walls along its border with Iraq and part of the border with Iran similar to the nearly completed one on its longest border, with Syria.
Ankara and Tehran have long sought closer relations, but their new meeting comes as Saudi Arabia's king is visiting Moscow.
Much of the regional international developments in the Middle East will probably be defined by their rivalry.