The House speaker is leading a congressional group that will focus on stability in the Middle East, the campaign against Islamic State and "Iranian aggression."
“We will crush anyone who opposes our national struggle,” President Recep Tayyip Erdoğan says in a warning to Kurdish activists.
The offensive has heightened tensions in the already complicated Syrian conflict, threatening to further strain ties between NATO allies Turkey and the U.S.
The move comes after the U.S. announces it will arm and train a Kurdish force to police Syria’s borders to ensure Islamic State does not re-emerge.
Ankara has launched a ground assault on a Syrian Kurdish-controlled enclave in Syria to thwart the establishment of a Kurdish corridor along the Turkish border.