Connecting to external API located in a different region from VPC EC2 is slow

Hi, We have been facing an issue where we are facing high latency when trying to invoke an external API(hosted on a different cloud provider in a different region) from an EC2 instance which is inside a private subnet connected to a NAT gateway. The reverse flow of the traffic is quite fast, as seen from the SCP and iperf3 tests. How do we circumvent this issue? Thanks