US national security adviser John Bolton has made "a very serious mistake" by demanding the safety of Kurdish fighters in Syria is guaranteed, Turkey's president has said.
Mr Bolton has been visiting Turkey to seek assurances over the Kurds who fought with US troops against Islamic State.
He has called it a "condition" for US President Donald Trump's much-criticised decision to pull out of Syria.
But Turkish President Recep Tayyip Erdogan shot down that request, telling parliament that Mr Bolton had "made a very serious mistake".
"Whoever thinks this way is also mistaken," he said.
Mr Erdogan said preparations for a new offensive against the Kurdish fighters – who the country views as terrorists – are complete "to a large extent".
The Turkish president did not meet Mr Bolton during his trip, sending his adviser Ibrahim Kalin instead.
Mr Kalin said Turkey would not seek permission from its allies to attack the fighters but was willing to coordinate operations.
MR Trump stressed on Monday that US troops would be leaving Syria at "a proper pace while at the same time continuing to fight ISIS", amid claims he was softening his approach because of heavy criticism.
The move – announced suddenly last month – prompted the departure of US defence secretary James Mattis.
Mr Kalin said US officials had told him during their meeting that the pull-out could happen within 120 days, but Mr Bolton has said there is no fixed timetable.
Talks with the US security adviser had centred on how the US would collect the weapons given to Kurdish fighters, as well as the future of US bases in Syria, Mr Kalin said.
Two dossiers were handed over, he added, one on Turkish help to Kurdish populations in Iraq and Syria, another on Kurdish militias' "criminal activities and human rights violations".
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Mr Bolton has previously that protecting allies in Syria is among "the objectives that we want to accomplish that condition the withdrawal" of troops.
US Secretary of State Mike Pompeo has also started an eight-country trip around the Middle East as both he and Mr Bolton try to get support for the withdrawal plan and reassure allies.