Lindsey Graham's preliminary cause of death revealed as aortic dissection after 'brief and sudden illness'

US senator Lindsey Graham's preliminary cause of death has been confirmed, as President Trump described the 71-year-old as 'one of the greatest people' he'd ever met.

Republican senator Graham died 'suddenly', his office confirmed on Sunday (July 12), following a long career and having represented South Carolina since 2003.

"On the evening of Saturday 11 July, US senator Lindsey Graham passed away from a brief and sudden illness," they wrote in a statement.

"Senator Graham’s family appreciates prayers at this time and asks for privacy during this incredibly difficult period."

Earlier today, preliminary findings by the Medical Examiner of the District of Columbia found that the senator likely died due to aortic dissection due to Arteriosclerotic Cardiovascular Disease - a life-threatening condition characterized by the tearing of the aortic wall.

Trump praised the senator in the wake of his death. (Jim WATSON / AFP via Getty Images)

Speaking with NBC at the weekend, President Trump noted that he had spoken with Graham just hours before the statement announcing his death was released.

He said: "He actually said he was tired, but he wanted to pass the SAVE America Act, and I said, 'Well, we’re going to get it done, Lindsey. We’re going to get it done. I’ll see you, like, soon.'"

Trump added: "If I had a problem, a real problem, I wouldn’t often ask. But if I had a problem with a Democrat, he could work it out.

"He was a great, he was a great politician, actually."

Writing on Truth Social in the wake of his death, the president further noted: "Senator Lindsey Graham, one of the greatest people and senators I have ever known, is dead!

"He was always working, and was a true American Patriot. Lindsey will be greatly missed!!! DETAILS AND ARRANGEMENTS TO FOLLOW. So sad!"

Trump issued a statement following the death of the senator. (Tasos Katopodis/Getty Images)

But the two did not always had an easy relationship.

Graham was previously a vocal critic of Trump, calling him a 'race-baiting, xenophobic, religious bigot' in 2015.

The next year, during the 2016 presidential election, he added: "If we nominate Trump, we will get destroyed... and we will deserve it."

But his attitude towards the president seemingly softened in recent years.

The senator had visited Ukraine the day before he died, with Ukraine's President, Volodymyr Zelenskyy, writing on social media: "I’m grateful to Lindsey for recognizing our warriors.

"He was a true defender of freedom and of the values that make our world safer."