Mevlut Cavusoglu said the plan, which also involves Russia, could be set in motion "at any moment" but it was up to the "will of the leaders".
Russia has not officially confirmed the deal, other than to say talks are under way with Turkey. The two countries back opposing sides in the conflict.
Rebels said they would meet Russian officials in Turkey on Thursday.
Turkey's state news agency had earlier reported the deal could come as early as Thursday evening.
The issue of which areas would fall under the ceasefire deal remains a possible stumbling block.
Earlier this month, Moscow and Ankara negotiated a ceasefire in Syria's second city, Aleppo, that led to tens of thousands of rebel fighters and civilians being evacuated from an enclave besieged by government forces.
Previous ceasefire initiatives this year brokered by the UN, or the US acting with Russia, quickly collapsed.
Fighting has continued elsewhere in Syria since the Aleppo evacuation, notably in the nearby town of al-Bab, where Turkey has been helping rebels fighting so-called Islamic State.
Speaking on Turkish TV, Mr Cavusoglu said Turkey and Russia would act as guarantors of the ceasefire deal, under which all foreign fighter groups would have to leave Syria.
"We are on the verge of an agreement with Russia," he said.
"If everything goes alright, we will make this agreement. Russia will be the guarantor of the regime [Syrian government]. Russia and Turkey are guarantors in the agreement being worked on in Ankara."
He added that there was "nothing final" on whether Iran, another military ally of Syrian President Bashar al-Assad,  would also sign it as a guarantor.
Russia's RT state TV channel said it was still waiting for confirmation from the Russian foreign ministry that a deal had been reached.
On Wednesday, Turkey's official Anadolu news agency cited an unnamed Turkish source as saying the ceasefire would exclude "terrorist organisations", without giving further details.
An official from the Islamist rebel coalition Ahrar al-Sham said there were fundamental disagreements over which areas would fall under the ceasefire deal.
Labib Nahhas singled out the rebel-held Eastern Ghouta area near Damascus, saying Russian attempts to exclude it from the truce were unacceptable.
Despite the obstacles, Turkey and Syria analyst Ilhan Tanir detected greater confidence among the negotiators after the Aleppo evacuation and last week's Moscow Declaration, a roadmap for Syria's future signed by Turkey, Russia and Iran.
"So this is kind of a third step and I think the parties have more confidence to work together for Syria," he told the BBC.
Diana Darke, a Middle East expert, said she was optimistic as Russia and Iran had achieved their war goals.
"Potentially everybody has finally reached the stage where they are ready," she told the BBC World Service's Newsday programme.
"They can see that there is nothing further to be gained. I mean Russia does not want to be sucked more and more in to the Syrian quicksand. They've got what they wanted. The same for Iran. The Syrian government itself is incredibly weak."
A plan to implement a ceasefire across Syria could be in place before the new year, Turkey's foreign minister says.