ANKARA (Reuters) -There is no talk of a ceasefire deal between Turkey and the U.S.-backed Syrian Democratic Forces (SDF) in northern Syria, contrary to a U.S. announcement, a Turkish defence ministry official said on Thursday.

The State Department had said a ceasefire round the city of Manbij was extended until the end of this week.

"As Turkey, it is out of the question for us to have talks with any terrorist organisation. The (U.S.) statement must be a slip of the tongue," the Turkish official, speaking on condition of anonymity, told reporters.

The SDF blamed Turkey for opposing international efforts to achieve a ceasefire. "The Turkish occupation and its mercenaries did not abide by this decision and continue their attacks on the southern front of the city of Kobani," it said in a statement, vowing to keep fighting and urging people in Kobani to carry arms.

Washington brokered an initial ceasefire between Turkey-backed Syrian rebels and the SDF last week after fighting broke out as rebel groups overthrew Bashar al-Assad.

The SDF is an ally in the U.S. coalition against Islamic State militants. It is spearheaded by the YPG, a group that Ankara sees as an extension of the Kurdistan Workers Party (PKK) militants who have fought the Turkish state for 40 years.

Turkey regards the PKK, YPG and SDF as terrorist groups.

The U.S. and Turkey's Western allies list the PKK as terrorist, but not the YPG and the SDF.

When asked if Ankara was considering another ground operation into northern Syria, the same Turkish official said that Turkey still sees a threat to its borders from north Syria.

"Our preparations and precautions as part of the fight against terrorism will continue until the PKK/YPG lays down its arms and its foreign fighters leave Syria," the official said.

Turkey believes forces of its ally the Syrian National Army paramilitary group will "liberate" YPG-controlled areas in north Syria, the official said, signalling that Turkey does not plan an imminent operation into the region.

(Reporting by Huseyin Hayatsever and Clauda Tanios; Editing by Daren Butler, Peter Graff and William Maclean)