Some top members of the U.S. Congress oppose the sale of the jets to Turkey despite support from the Biden administration for the sale.
The U.S. lawmakers objecting to the sale cite Turkey's deteriorating human rights track record and Syria policy. But recently, Ankara's refusal to ratify NATO membership of Sweden and Finland is emerging as a more central reason in their opposition.
"(Turkish President Tayyip) Erdogan's ... repeated attacks on our Syrian Kurdish allies, and continued cozying up to Russia — including delaying Sweden and Finland's NATO membership — remain serious causes for concern," Democratic Senator Chris Van Hollen said in a statement.
"As I’ve said before, for Turkey to receive the F-16s, we need assurances that these concerns will be addressed," he said.
Reporting by Humeyra Pamuk and Simon Lewis, additional reporting by Huseyin Hayatsever in Ankara, Patricia Zengerle in Washington for Reuters.