Iranian President Hassan Rouhani paid a visit to Turkey on June 9, 2014, a year after he was elected president. This was a significant visit to reform the relations with Iran that were broken since they supported Syrian President Bashar Assad who has used chemical weapons in Syria. However, some other important problems were lying at the root of Iran-Turkey relations apart from Syria and Assad that were not publicly expressed. I had listed those problems two days before Rouhani's visit in my Daily Sabah column.1. Turkey is conducting the reconciliation process to disarm the PKK. Iran does not favor the process to be accomplished, and Ankara is aware of this. 2. Iran is upset with the relations between Turkey and the Iraq Kurdistan Regional Government (KRG). It especially tries to prevent the steps taken to introduce Kurdish oil to the world market through Turkey. 3. Iran is in cooperation with the Democratic Union Party (PYD) in northern Syria, which is a wing of the PKK. It even provides the PYD with weapons.Almost 10 months have passed since I wrote that column. Now, President Recep Tayyip Erdoğan is expected to pay a visit to Tehran on April 7. Before Erdoğan's scheduled visit to Tehran, let's review the problematic parts of Turkey-Iran relations from Ankara's point of view. First I would like to handle the visible problems. Over the course of 10 months, Iran's aggressive sectarian and expansionist policies have gone beyond Syrian borders. Tehran's support for Assad was already one of the most significant problems. Iran used the chain of operations that was initiated by the international coalition against the Islamic State of Iraq and al-Sham (ISIS) to expand its sphere of influence. It joined the operations that the Iraqi army began in order to save Mosul and neighboring cities from ISIS with the Shiite militia it supported. Iranian commanders posed for the cameras both in Syria and Iraq. This aggressive stance by Iran turned the fight against ISIS into a sectarian debate. This uneasiness was clearly felt by the KRG in both northern Iraq and other actors of the region. KRG Prime Minister Nechirvan Barzani wanted the Turkish military to join in on the Mosul operation due to Iran's aggressive attitude.While Iran's aggressive stance in Iraq and Syria was also upsetting Ankara, the coup attempts of the Iran-backed Houthis in Yemen caused Tehran to reach the tipping point. The coalition formed by Arab countries led by Saudi Arabia made a military intervention in Yemen. This was the expression of the accumulated anger toward Iran's regional policies. Erdoğan reflected this accumulation of anger with his remark: "Iran must leave Syria, Iraq and Yemen." Ankara announced that it would back up the coalition intervening in Yemen. So far I wrote the visible reasons of the rising tension between Ankara and Tehran. Now I would like to mention the other side of the coin that is worrying Ankara.Iran's approach to the reconciliation process has not changed. It still does not wish for the success of the process since it believes that the PKK's disarmament in Turkey would lead it to target Iran. Therefore, it blockaded the Qandil Mountains in Iraq, the headquarters of the PKK. It tries to persuade PKK administrators by conducting negotiations with them. When persuasion efforts do not yield results, it resorted to weapons, bombing the Qandil Mountains. We witnessed the latest instance of this a few days before the historic call of disarmament made to the PKK at Dolmabahçe Palace in late February.There is no change in Iran's approach to the KRG. Tehran continues oppressing Irbil to keep distance from Turkey in political and economic terms including the energy issues. Also, Iran tried to take steps that would undermine Barzani. Some allegations we have are parallel to the statements of Jordan's former information minister, Saleh al-Qallab. According to some reports from northern Iraqi media, Qallab alleged that Iran was involved in various initiatives to take out KRG President Massoud Barzani. Iran does not favor Barzani since Barzani views Turkey as a strategic partner.Erdoğan is to visit Iran in the midst of these developments. From whichever point you look at the picture, the results of the visit will profoundly affect Turkey-Iran relations and the future of the region.