Pompeo says US did not approve Turkey's Syria offensive
This week, the White House announced a US withdrawal from the country, which was widely seen as giving Turkey a green light for the military campaign.
But Pompeo also said that Turkey had "legitimate security concerns" about the situation in Syria, where the Syrian Democratic Forces (SDF) - dominated by the Kurdish People's Protection Units - have established a foothold in the country.
"They have a terrorist threat to their south," he said.
Trump has warned of tough sanctions if Turkey does not conduct the operation "in as humane a way as possible".
Republican Senator Lindsey Graham said he and Democrat Chris Van Hollen are introducing legislation that would freeze all US assets of Turkey's political leadership - including President Recep Tayyip Erdogan, his vice president and the defence minister.
It would also impose sanctions on entities that do business with Turkey's military, or with oil and gas companies that service its armed forces.
Graham and several other US lawmakers are furious over President Donald Trump's sudden military withdrawal from positions in northern Syria, blasting the move as a betrayal of Kurdish forces who for years have helped fight Islamic militants, and as an effective green light for Turkey to launch its long-planned offensive.
"While the Administration refuses to act against Turkey, I expect strong bipartisan support" for the measure, Graham said on Twitter.
Turkey has not yet launched a ground offensive into Syria, but had shelled and bombed the areas that are set to be the target of the largely Syrian rebel force.
Dubbed "Operation Spring of Peace", The New Arab revealed this week plans of the operation, including the targeting of Tal Abyad by the Turkish-Syrian force in the first stage of the offensive.
Human rights groups are concerned by civilian casualties and flights of people from areas targeted by Turkey.
Agencies contributed to this story
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