At a February 5 meeting of the Justice and Development Party, Deputy Prime Minister Bulent Arinc delivered a blistering critique of Iran's policy of support for Syrian President Bashar al-Assad despite the Syrian government's bloody crackdown on opposition strongholds.

"I am addressing the Islamic Republic of Iran: I do not know if you are worthy of being called Islamic," Arinc said, according to the Anatolia state news agency. "Have you said a single thing about what is happening in Syria?"

This tone represents quite a change from 2009, when Turkish President Abdullah Gül was among the first world leaders to congratulate Iranian President Mahmoud Ahmedinejad on his contested reelection, or in 2010, when Ankara put its relationship with Washington on the line by voting against Iran sanctions in the United Nations Security Council.

News coverage also comes with a sharper edge. The Turkish press has increasingly started running articles that cast suspicions on Iran's intentions in the region and in Turkey, with some recent reports and columns suggesting that the Revolutionary Guards were planning attacks inside Turkey and that Iran is smuggling weapons through the country to Syria.

Hugh Pope, Turkey project director for the Brussels-based International Crisis Group, and one of the authors of a report on Iran and Turkey to be released on February 23, believes that Ankara's more critical stance toward Iran indicates that "[t]he more hawkish faction in Ankara, the kind that thinks Iran is crossing the line in Syria and Iraq, is becoming more pronounced . . ."

Turkish Prime Minister Recep Tayyip Erdoğan "feels personally burned by the Iranians . . . " Pope commented. "Erdoğan likes to have wins and the risks he took for Iran did not pay off, either in the US or Iran."

But the two sides' mutual wariness is not always consistent. An Iranian general earlier threatened a retaliatory strike if Turkey hosted a North Atlantic Treaty Organization missile radar, but, nonetheless, Tehran has also proposed Istanbul as a possible site for another round of talks about Iran's nuclear research program.

Much of the Turkish-Iranian sparring is done instead via proxies. In Iraq, Turkey's neighbor to the south, Ankara's support for the Sunni Iraqiya alliance resulted in a falling out with Iranian-backed Prime Minister Nouri al-Maliki, who has since gone on to accuse Ankara of "interfering" in Iraq's internal affairs.

"There is quite a strong and growing rivalry between the two countries inside of Iraq, and it stems from having genuinely different interests," said Sean Kane, a former UN official in Iraq and the author of a 2011 report on Turkish-Iranian competition in Iraq for the United States Institute of Peace.

"For Turkey, having a strong Iraq has historically been a bulwark against Kurdish separatism and Iranian adventurism. Iran looks at all of this very differently. A strong Iraq is a rival, and historically has been a hard security threat."