US Vice President Mike Pence arrived in Turkey on Thursday in a bid to secure a ceasefire to halt the Turkish offensive in Syria.
Secretary of State Mike Pompeo arrived earlier on a separate plane. They are due to meet with Turkish President Recep Tayyip Erdogan.
The visit comes a day after Erdogan firmly ruled out any negotiations with Kurdish militants in Syria, saying their only option was to lay down arms and retreat.
The United States has demanded a ceasefire in Turkey's more than week-old operation in northern Syria.
President Donald Trump, facing with mounting criticism over the abrupt pullout of US troops, has denied he gave Erdogan a "green light" to launch the offensive.
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