Veteran US senator John McCain has chosen to end his medical treatment for brain cancer, his family have said.
The former presidential candidate, who turns 82 next week, revealed he had been diagnosed with an aggressive form of the disease last year.
In a statement, Mr McCain's family said he had "surpassed expectations for his survival", but the progress of the cancer and his age "render their verdict".
"With his usual strength of will, he has now chosen to discontinue medical treatment," they said.
In a post on Twitter, Mr McCain's wife Cindy said: "I love my husband with all of my heart. God bless everyone who has cared for my husband along this journey."
Mr McCain's daughter, TV host Meghan McCain, said her family is "deeply appreciative of all the love and generosity" they have received over the past year.
Mr McCain was the Republican Party's presidential candidate when he lost to Barack Obama in the 2008 presidential election.
He also sought the Republican presidential nomination in 2000 but was beaten by George W Bush.
Mr McCain is in his sixth term as a senator for Arizona, having first been elected in 1986, but has been away from Washington DC since December.
The military veteran spent more than five years as a prisoner of war in Vietnam after his plane was shot down in 1967.
He was tortured and suffered two broken arms, a broken leg, a broken shoulder and numerous stab wounds during the ordeal.
He had a running feud with US President Donald Trump that grew heated in 2015 when he said the tycoon's candidacy had "fired up the crazies".
Shortly after his diagnosis, Mr McCain voted against a Trump-backed bill that would have repealed the healthcare law pushed through by Mr Obama.
Mr Trump caused controversy after claiming Mr McCain was "not a war hero", saying: "I like people who weren't captured."
The president signed a military policy bill named in honour of Mr McCain earlier this month, but failed to mention the senator in remarks at the signing ceremony.
Messages of support for Mr McCain poured in following news that he has opted to halt his treatment.
Former Republican presidential candidate Mitt Romney said: "No man this century better exemplifies honour, patriotism, service, sacrifice, and country first than Senator John McCain.
"His heroism inspires, his life shapes our character."
Former US secretary of state John Kerry called his fellow Vietnam veteran "a brave man", while Republican Senate leader Mitch McConnell said he was "very sad" to hear the news.
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In their statement, Mr McCain's family said they were "immensely grateful for the support and kindness of all his caregivers over the last year".
They also praised "the continuing outpouring of concern and affection from John's many friends and associates" and the "many thousands of people who are keeping him in their prayers".