Turkey's Hurriyet newspaper quoted Erdoğan as saying that NATO has a responsibility to protect the country's borders under Article 5 of the North Atlantic defence pact, which allows for a common response to an attack on the territory of a member state.
Ankara has urged the UN Security Council to adopt a resolution that would protect the Syrian people, saying Damascus had not kept its troop withdrawal pledge and has increased the violence.
Gunfire blamed on Syrian forces hit border camps in Turkey twice this week, with several injuries reported. Turkey is hosting nearly 25,000 Syrian refugees who have fled violence at home.Damascus agreed to a Security Council-backed deadline of 10 April to withdraw troops Syrian towns and stop using heavy weapons against civilians. That deadline was supposed to be followed by a full cease-fire by the Syrian army and opposition forces today (12 April), but fierce fighting has continued.
UN and Arab league envoy Kofi Annan, at a news conference in Tehran on Wednesday, urged Syrian President Bashar al-Assad's long-time ally Iran to help resolve the violence and warned of "unimaginable consequences" if it worsened further.
Iranian President Mahmoud Ahmadinejad, quoted by state news agency IRNA, urged an end to violence but accused the NATO powers of expansionist ambitions in the Middle East and said Tehran's Syrian ally should not be put under pressure.
"NATO is not ashamed to say it wants to dominate the region and is trying to extend its domination eastward," IRNA said, quoting Ahmadinejad as insisting: "The implementation of any plan in Syria should be free of pressures and interference, and all violence in that country should be stopped."
Iran has backed Syria, the only Arab nation to support Iran in its 1980-'88 war with Iraq and the conduit for Iranian arms to Lebanon's Shi'ite Muslim Hezbollah movement.
Syria, where Assad's Shi'ite-rooted Alawite minority dominates a Sunni Muslim majority, has become an arena for a sectarian-tinged regional contest between Shi'ite Iran and Sunni Arab rivals aligned with the West and led by Saudi Arabia.
British Prime Minister David Cameron, speaking after the lull was reported, said Assad was failing to abide by the terms endorsed by the Security Council last week: "I feel an immense sense of frustration because the world has come together behind this Kofi Annan plan," he told the BBC.
"This is a plan, remember, that is not just backed by those of us who have been pushing for action on Syria, it's also backed by China and Russia. And yet Assad is deliberately flouting it."
In an indication of how the Western leaders who intervened to help rebels topple Muammar Gaddafi in Libya last year are reluctant to do likewise in Syria, Cameron made it clear that the main thrust of Western efforts would be to persuade Moscow and Beijing to accept tighter punitive sanctions.
"Now is the time to say to the Russians and Chinese, look at the man we are dealing with, look at the appalling way he is behaving," Cameron said. "We need to go back to the UN and tighten the pressure, tighten the noose."
The opposition Syrian National Council is also lobbying for a strong international ultimatum to Assad if the peace fails.
Russia and China, alarmed by the way last year's Security Council resolution on Libya led to military intervention against a sovereign state, have vetoed attempts to penalise Assad, although the United States, European Union and Arab League have imposed their own economic and political sanctions.