Approved traffic moves the other way, as Turkey and other nations that oppose Assad send logistical and humanitarian aid to Syrian rebels and civilians. While Turkey says it is not arming the insurgency, Syrian rebels have told The Associated Press they receive some weapons and ammunition from the Turkish side with only sporadic interference from border patrols. According to rebels, these weapons are bought with funding from rich Syrians or sympathetic Gulf Arabs.

Fences are down and cars can cross in some parts adjoining Syria's Idlib province, an opposition stronghold.

The first mines on the Syrian border were planted after smugglers killed two customs agents in 1956. Turkey laid more mines in the 1980s and 1990s, at the height of its war with the rebel Kurdistan Workers' Party, or PKK, which was backed by Syria. Turkey is again worried about possible infiltration by Kurdish rebels who are cheered by an autonomy grab by their ethnic brethren in Syria.

The Turkish defense ministry told the AP it started evaluating bids from demining companies in July and would sign contracts once the assessment is complete.

"Developments in Syria to this day have not affected our plans or work," the ministry said. NATO said it is assisting with "technical preparations" for the mine clearance.

Cenk Sidar, managing director of Sidar Global Advisors, a Washington-based consultancy, said he believed that Turkey would sign contracts but wait until the Syrian civil war is resolved.

"According to plans, the government will build electronic border surveillance systems simultaneously with the demining. Even this seems too risky at this point," Sidar wrote in an email. "It may take a few years, and some qualified/selected firms may change their pricing or conditions due to the increasing instability."

Between 2010 and 2011, a Turkish firm, Nokta, and a partner from Azerbaijan cleared more than 1,200 mines around an archaeological site, Karkemish, on the Syrian border. They found anti-tank mines and M14 mines known as "toe poppers." It was hard to work with metal detectors because the soil also contained remnants of coins and other ancient fragments; some mines had to be dug out by hand rather than detonated to avoid damaging cultural treasures.

If you liked this article you might like

What's Behind the Surge in Energy Stocks

Hillary Clinton Says Prosecuting Individuals is Key to Wall Street Reform