Janet Yellen, head of the US Federal Reserve, told a Congressional hearing that the US would be adversely impacted if Brexit passes.

Sen.Tom Cotton (R-Ark.) is vowing that he’ll fight any attempt to punish the United Kingdom if it votes to leave the European Union this week.

Cotton spoke on the Senate floor Tuesday against politicians, including President Obama, and economists who have warned of dire economic consequences if the U.K. leaves the EU, called “Brexit.”

“The American people will stand with Britain, in or out of the EU, and will stand against punitive retaliation against the British people,” said Cotton, promising to defend the U.S. and U.K.’s close military and economic ties.

“Just as I’ll do everything in my power to preserve our special relationship against [European] meddling, so I’ll do the same with any administration who doesn’t fully appreciate that relationship,” he said.