ISTANBUL (Reuters) - Syrian President Bashar al-Assad has told Turkey it will pay a heavy price for backing rebels fighting to oust him, accusing it of harboring "terrorists" along its border who, he said, would soon turn on their hosts.
In an interview with Turkey's Halk TV due to be broadcast later on Friday, Assad called Turkish Prime Minister Tayyip Erdogan "bigoted" and said Ankara was allowing terrorists to cross into Syria to attack the army and Syrian civilians.
"It is not possible to put terrorism in your pocket and use it as a card because it is like a scorpion which won't hesitate to sting you at the first opportunity," Assad said, according to a transcript from Halk TV, which is close to Turkey's opposition.
"In the near future, these terrorists will have an impact on Turkey and Turkey will pay a heavy price for it."
Turkey, which shares a 900-km (560-mile) border with Syria and has NATO's second-largest deployable armed forces, is one of Assad's fiercest critics and a staunch supporter of the opposition, although it denies arming the rebels.
It shelters about a quarter of the 2 million people who have fled Syria and has often seen the conflict spill across its frontier, responding in kind when mortars and shells fired from Syria have hit its soil.
It has allowed rebel fighters to cross in and out of Syria but has grown alarmed, along with Western allies opposed to Assad, by divisions among their ranks and the deepening influence of radical Islamists in Syria.
Last month, the al Qaeda-affiliated Islamic State of Iraq and the Levant seized Azaz, about 5 km (3 miles) from the border with Turkey, and has repeatedly clashed with the local rebel Northern Storm brigade since then.
"Right now, Syria is headed for a sectarian war," Erdogan said in an interview on Turkish television late on Thursday.
"This is the danger we are facing."
Turkey has bolstered its defenses and sent additional troops to the border with Syria in recent weeks. Its parliament voted on Thursday to extend by a year a mandate authorizing a military deployment to Syria if needed.
Russia, Assad's most powerful ally, pointed to the seizure of Azaz as evidence Islamists are gaining the upper hand and said states that want his overthrow had helped make that happen.
"The balance of power among the opposition fighting forces is stacking up decisively in favor of the Islamists," Foreign Ministry spokeswoman Maria Zakharova said in a statement.
"We are by no means gloating about this - clearly a dangerous new act in the bloody tragedy is unfolding.
"We warned of such a turn of events at the very beginning of the Syrian epic, when our opponents, hoping for the regime's swift fall ... were ready to support any forces calling for the government's overthrow."
Assad accused Erdogan, whose AK Party has its roots in conservative Islamist politics, of having a sectarian agenda.
"Before the crisis, Erdogan had never mentioned reforms or democracy, he was never interested in these issues ... Erdogan only wanted the Muslim Brotherhood to return to Syria, that was his main and core aim," he said.
Erdogan's government strongly denies any such agenda.
His aides point to his cultivation of good relations with Assad for years before the conflict and say Turkey does not see Syria's Sunni Muslims and its Alawite sect, an offshoot of Shi'ism to which Assad belongs, as fixed blocs.
Assad said he had not yet decided whether to run in presidential elections next year because the situation on the ground was changing rapidly, adding that he would only put himself forward if Syrians wanted him to. The picture will become clearer in the next 4-5 months, Assad said.
The United Nations estimates that more than 100,000 people have died since the uprising against Assad began in March 2011 and has been notified of at least 14 chemical attacks.
The U.N. Security Council adopted a resolution last week that demands the eradication of Syria's chemical weapons and endorses a plan for a political transition in Syria agreed on at an international conference in Geneva last year.
U.N. Secretary-General Ban Ki-moon said after the vote that major powers hoped to hold a second peace conference on Syria in mid-November in Geneva.
In his interview, Assad again denied his forces had used chemical weapons and blamed such attacks on the rebels. Asked whether he expected the Geneva process to accelerate if Syria handed over its chemical weapons, Assad said he saw no link.
"Practically these issues are not related. Geneva II is about Syria's own domestic political process and cutting neighboring countries' weapons and financial support to terrorists," he said.
Additional reporting by Humeyra Pamuk and Orhan Coskun in Ankara and Steve Gutterman in Moscow; Writing by Nick Tattersall; Editing by Andrew Roche