WASHINGTON • Veteran senator and war hero John McCain - a towering figure in American politics for decades - has stopped treatment for brain cancer, his family announced, one year after the Republican went public with his diagnosis.

The announcement last Friday signals the beginning of the end of a tough battle with glioblastoma - and of a storied life that took the Naval Academy graduate from a Hanoi prison to the doorstep of the White House.

"The progress of disease and the inexorable advance of age render their verdict," the 81-year-old senator's loved ones said in a statement.

"With his usual strength of will, he has now chosen to discontinue medical treatment."

Prime Minister Lee Hsien Loong said on Facebook yesterday that Mr McCain's decision to end treatment "must not have been easy, but he is not one to shy away from adversity".

PM Lee added: "McCain has been a friend and supporter for Singapore for many years. I'm keeping him and his family in my thoughts. Take care, John."

Mr McCain has spent more than three decades in the upper chamber of Congress, looming large in debates over war and peace and the moral direction of the nation.

The Navy fighter pilot spent years as a prisoner of war in Vietnam after being shot down while on a bombing mission over Hanoi.

He lost the 2008 presidential election to Mr Barack Obama, and was pilloried for selecting controversial Alaska politician Sarah Palin as his vice-presidential running mate.

"No man this century better exemplifies honour, patriotism, service, sacrifice, and country first than Senator John McCain," said fellow Republican Mitt Romney.

"His heroism inspires, his life shapes our character. I am blessed and humbled by our friendship."

Mr McCain has, since 2016, been a rare and outspoken Republican critic of President Donald Trump.

Known for his combustible temper, he has accused the 45th president of "naivete" and "egotism" and of sympathising with autocrats.

Mr McCain has not been on the Senate floor in months, remaining at his Arizona home while being treated for glioblastoma - the same form of brain cancer that took the life of another Senate giant, Democrat Ted Kennedy, in 2009.

"I love my husband with all of my heart. God bless everyone who has cared for my husband along this journey," his wife Cindy said.

His daughter Meghan thanked the public for an outpouring of support.

AGENCE FRANCE-PRESSE