A number of war veterans lobbying for the return of the Balangiga Church Bells taken by the USA as war booty during the Philippine-American War were reportedly seeking McCain's help in the years before his death.
Mark Corallo, a former spokesman for Trump's legal team and a longtime Republican strategist, said of Trump's reaction to McCain's death that "at a time like this, you would expect more of an American president when you're talking about the passing of a true American hero".
Five-term Senator John McCain died on Saturday after a year-long battle with a brain cancer, he was 81.
"History does rhyme", Preet Bharara, the former USA attorney from the Southern District of NY, said in a tweet.
Speaker Paul Ryan also in a tweet said: "John McCain was a giant of our time - not just for the things he achieved, but for who he was and what he fought for all his life".
President Trump offered his "deepest sympathies and respect" to the McCain family. Citing family friends, CNN reported that McCain told his family he did not want Trump to attend his funeral. We know that his flame lives on, in each of us.
But Trump instead said he preferred to post a short statement via Twitter, and the White House statement was not released.
Throughout his career in the legislature, McCain was known for being a moderate conservative who disagreed with his party on certain issues.
"John McCain was a man of deep conviction and a patriot of the highest order".
When Trump announced his candidacy for the Republican presidential nomination in June 2015, suggesting that many Mexican immigrants were criminals and "rapists", McCain denounced him for using language that "fired up the crazies".
When Republicans took control of the Senate in 2015, McCain embraced his new influence as chairman of the Armed Services Committee, pushing for aggressive US military intervention overseas and eager to contribute to "defeating the forces of radical Islam that want to destroy America". "Americans will be forever grateful for his heroic military service & steadfast integrity".
From overseas, Canadian Prime Minister Justin Trudeau said McCain's "lifetime of public service" was "an inspiration to millions", while Israeli Prime Minister Benjamin Netanyahu praised him as "a great American patriot" whose "support for Israel never wavered".
Former vice president Al Gore said he always admired how the senator "would work to find common ground, no matter how hard". But he and running mate Sarah Palin lost to Barack Obama. John McCain was a maverick and a fighter, never afraid to stand for his beliefs.
Schumer, who serves as the Senate's minority leader, said he will introduce legislation to rename the Russell Senate office building in Washington in McCain's memory.
John Sidney McCain III was born August 29, 1936, in the Panama Canal Zone and into a family whose military lineage included an ancestor who served as an aide to Gen George Washington during the Revolutionary War.
Sen. Lindsey Graham, a very close friend of McCain at the senate, said: "America and Freedom have lost one of her greatest champions".
Mr McCain and former Senator Kerry played important roles in the normalisation of bilateral relations in 1995.
"Another anti-China warrior is down, godspeed, you can finally rest, there's no China in heaven", wrote one user on the Twitter-like Weibo.
Sen. Bernie Sanders tweeted: "As you go through life, you meet few truly great people".
Sen. John McCain arrives for the funeral of Sen. Democrat Senator Chuck Schumer hailed him as a "truth-teller" with "unsurpassed" dedication to the U.S. and its military.