U.S. Senator Lindsey Graham, a longtime Republican lawmaker from South Carolina and one of President Donald Trump’s closest allies in Congress, has died at the age of 71 following what his office described as a “brief and sudden illness.”

In a statement released early Sunday, Graham’s office said, “On the evening of Saturday, July 11, U.S. Senator Lindsey Graham passed away from a brief and sudden illness. Senator Graham’s family appreciates prayers at this time and asks for privacy during this incredibly difficult period.”

The veteran senator had been in Ukraine just one day before his passing.

First elected to the U.S. Senate in 2002, Graham became one of the most influential Republican voices on foreign policy. Although he was initially critical of Donald Trump during the 2016 presidential campaign, he later became one of Trump’s staunchest supporters and closest allies in Congress. He was also a steadfast supporter of Israel, consistently advocating for strong U.S.-Israel relations and backing military aid and security cooperation.