World leaders and senior political figures convened in Washington for the memorial of the long-serving US senator Lindsey Graham, remembering the “swashbuckling” South Carolina Republican “a true American original” whose embrace of “America First” never softened his advocacy for a staunch interventionist US foreign policy.

Prominent Republicans paid tribute to Graham, a polarizing figure and onetime rival turned stalwart ally of Donald Trump who championed the US-Israel war on Iran. He was a prominent voice in the anti-abortion movement and a unwavering supporter of Israel, serving as one of Capitol Hill’s most outspoken foreign policy hawks.

“He died doing the work he was born to do, he was truly a great politician, serving the country he loved to serve so deeply,” Trump said of Graham in his eulogy at the National Cathedral.

“He went out at the peak of his career, the top of his game as a legend that every one of us, many of us here today, blessed to know him and a friend that none of us will ever forget,” he added.

Trump took the opportunity to reiterate his support for Graham’s sister, Darline Graham, who was appointed to the late senator’s seat for the remainder of his term. And he focused on Graham’s foreign policy record as a war hawk.

“I will tell you, he never saw a war that he didn’t like. Only his true friends would understand that. But he wanted it for the good of our country,” he said.

The president, who ran against Graham in the 2016 presidential election, admitted that “Lindsey and I did not exactly get off to the best of starts.”

Recalling his leaking of Graham’s phone number to the public after Graham called him a “jackass” during the presidential race, Trump said: “It was Lindsey who had the last laugh because while I blew up his phone all for one day, we became great friends, and Lindsey did not stop calling me for the next 10 years. It was not easy.”

Speaking during a ceremony earlier on Tuesday inside the Capitol Rotunda, the US Senate majority leader, John Thune, hailed Graham as a “fierce defender of Ukraine”, following its full-scale invasion by Russia in 2022, and a “powerful voice for the [anti-abortion] movement”.

“I feel his absence every day, and I know my colleagues do as well,” Thune, growing emotional, continued. “I look forward to the days when you make us laugh again.”

Darline Graham, who was sworn in earlier this month, attended both services. She is running in the Republican primary to permanently succeed him.

Graham died suddenly earlier this month, aged 71, shortly after returning to Washington from a trip to Kyiv. The Ukrainian president, Volodymyr Zelenskyy, and Israeli prime minister, Benjamin Netanyahu, are due to attend an afternoon service for Graham at Washington National Cathedral.

JD Vance, the US vice-president, credited Graham with the successful confirmation of Brett Kavanaugh to the US supreme court in 2018, which helped conservatives secure a supermajority on the bench within two years. “I believe that he saved that nomination,” Vance said.

Vance paid tribute on Tuesday morning to Graham as someone “who could disagree with you without being disagreeable”.

“I choose to remember Lindsey Graham as a person who could fight with you on one issue, but fight for you on another issue,” he said. “I remember Lindsey Graham as a man who loved people, and because he loved people, he was willing to reason with them, to respect them and ultimately to persuade them.”

“May God rest the soul of Senator Lindsey Graham, a true American original,” he said.

A former air force lawyer who served in the air force reserve while in Congress, Graham was elected to the House of Representatives in 1994 and served as a manager during Bill Clinton’s 1999 impeachment trial before winning a Senate seat in 2002. Weeks before his death, Graham defeated a field of challengers to win the Republican nomination in his bid for a fifth term.

On Wednesday, in Graham’s home state, ceremonies will begin with services and an F-16 flyover at the South Carolina state house in Columbia, followed by a procession to First Baptist church for a public service.

A private family burial will take place in Pickens county, home to Central, the small town where Graham and his younger sister and Senate successor, Darline, were born.