The US has imposed sanctions on Turkish ministries and senior government officials in response to the country’s military offensive in northern Syria.
President Donald Trump also phoned his Turkish counterpart Recep Tayyip Erdogan to demand an immediate truce, Vice-President Mike Pence said.
Mr Pence said he would travel to the region “as quickly as possible”.
The move comes after criticism of a US troop withdrawal from the region which some say gave Turkey a “green light”.
The Turkish offensive, which began last week, aims to push the Kurdish-led Syrian Democratic Forces (SDF) from the border region. Turkey considers the biggest militia in the SDF a terrorist organisation.
The Turkish government wants to create a “safe zone” in the area, where it can resettle up to two million Syrian refugees currently in Turkey.
Many of them are not Kurds and critics warn this could lead to ethnic cleansing of the local Kurdish population.