Iranian Foreign Minister Mohammad Javad Zarif on Tuesday postponed a scheduled visit to Turkey, officials said, with mystery surrounding the reason for the last-minute cancellation.
The visit had been expected to touch on the Syria crisis, which has caused profound disagreements between Tehran and Ankara with Iran one of the last allies of Turkey's arch foe President Bashar al-Assad.
"There has been a change in the programme," the Turkish official said, without giving any reason.
Iran's official IRNA agency also cited an Iranian foreign ministry official as saying the visit had been postponed due to "scheduling problems."
Zarif had been due to meet Turkey's leaders in the capital Ankara but there were conflicting reports over whether he was to have met President Recep Tayyip Erdogan.
Instead, Zarif would travel to Lebanon on Tuesday, and then to Syria a day later, Iranian foreign ministry spokeswoman Marzieh Afkham said in Tehran.
Adding to the mystery, Turkish opposition daily Cumhuriyet on Tuesday unexpectedly published a page-long article by Zarif containing a possible criticism of Turkish foreign policy.
The newspaper is known as an opponent of the policies of the ruling Justice and Development Party (AKP), with Erdogan repeatedly locking horns with its editor-in-chief Can Dundar.
In the piece, Zarif criticised US policies in the Middle East, and blamed the emergence of extremist groups, including the Islamic State (IS) group, on US-led war in Iraq in 2003.
He also said that the IS group was fed by the chaos and instability after the Iraqi invasion.
- 'Veiled criticism' -
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"Extremist elements found a convenient environment during the Syrian crisis with the support they received from individuals, organisations and governments in the region and turned into a giant structure in pursuit of fake causes and ideals," the minister wrote.
"Today, those elements are threatening even their own founders and supporters."
His comments could be seen as veiled criticism of Turkey, which has been accused of failing to do enough to halt the rise of Islamic State and even secretly colluding with the group.
Ankara vehemently denies the claims.
A NATO member, Ankara had long refused to participate actively in the US-led anti-IS operations for fear of supporting the Kurdish fighters battling the jihadists on the border in Syria.
But it changed its position after a deadly July 20 bombing, blamed on IS, that killed 32 people in the Turkish border town of Suruc.
Turkey then agreed to open a southern airbase to US and coalition forces for anti-IS raids and also began its own strikes on the jihadist group.
Shiite Iran has urged overwhelmingly-Sunni Turkey to respect Syria's sovereignty in its bombing of IS targets.
In a telephone call with Erdogan last week, Iranian President Hassan Rouhani suggested Turkey should "coordinate" its attacks with both the Syrian and Iraqi governments.
In the article, Zarif also criticised US-led "Greater Middle East" project as preparing the ground for military interventions in the region.
Turkey was once considered a key actor in the initiative during the presidency of George W. Bush, seen as a predominantly Muslim country with a working democracy.