Houston: Former US presidents, family and friends today bid a tearful farewell to the former first lady Barbara Bush at a private funeral at the nation's largest Episcopal church and remembered her as the "first lady of the greatest generation."

The private funeral was held at the St Martin's Episcopal Church here a day after more than 6,000 people paid their respects to the woman known by many as "America's matriarch."

Around 1,500 invited guests including four former presidents and three former first ladies, as well as the current first lady, attended the funeral to honour the life and legacy of Barbara Bush.

Barbara Bush, who died on Tuesday at the age of 92, had requested in her last wishes a modest funeral at the Gothic-style cathedral, where she and her husband, former President George H W Bush, were devoted members for decades.

First lady Melania Trump attended today's service on behalf of the first family, White House deputy press secretary Lindsay Walters said in a statement.

"To avoid disruptions due to added security, and out of respect for the Bush family and friends attending the service, President Trump will not attend”, the statement said.

In 2016, then President Obama did not attend the funeral of former first lady Nancy Reagan, while his wife did. Sitting presidents have rarely in recent decades gone to the funerals of former first ladies, according to FactCheck.org, a project of The Annenberg Public Policy Center in Philadelphia.

Trump, who is at his Mar-a-Lago resort in South Florida for the weekend, extended his "thoughts and prayers" to the Bush family via Twitter and said he planned to watch Barbara Bush's funeral service from the "Southern White House."

Bush was remembered as a woman who represented the best of the World War II generation.

"Barbara Bush was the first lady of the greatest generation," presidential historian Jon Meacham, a friend of the Bush family, said in a eulogy at the service in Texas that drew signatories from across the nation and around the world.

Meacham recalled the snowy-haired former first lady's "long and consequential life," not least her promotion of literacy and her devilish sense of humor.

"She was candid and comforting," Meacham said, adding that she "kept everything and everyone together."

Four of the five living ex-presidents attended the funeral service, including former President Barack Obama and his wife, former first lady Michelle Obama, as well as former President Bill Clinton and his wife, former Secretary of State and first lady Hillary Clinton. The Clintons' daughter, Chelsea Clinton, was also in attendance.

Following the service, Bush's grandsons carried the casket out of the church. The Bush family then drove by motorcade about 70 miles to the grounds of the George H W Bush Presidential Library in College Station, Texas, where she will be buried.

She will be laid to rest next to her daughter Robin, who died of leukemia in 1953 when she was three years old.

Earlier at the public viewing Friday night, attendees received a remembrance card with a statement from Bush that read, George Bush and I have been the two luckiest people in the world, and when all the dust is settled and all the crowds are gone, the things that matter are faith, family and friends.

Mourners gathered at St Martin's Episcopal Church in Houston to celebrate the life of the matriarch of the Bush family, who was the wife of a president and the mother of another.

While today's invitation-only service was for family and friends, a viewing was held yesterday for the public, where people paid their respects at the church until midnight.

Barbara Bush's husband, former president George H W Bush, made a last minute decision to greet mourners at the church.

On Saturday morning ex-president Bush hosted a reception for the visiting dignitaries before the private service.

Meanwhile, the church began to fill with less-recognizable friends of the family, including former staffers and Secret Service members who protected them for more than three decades.

Many of the women in attendance eschewed black in favour of a vibrant royal blue, Bush's signature colour. The mood inside the church was celebratory rather than sad full of hugs and kisses akin to a reunion of old friends.

As part of the ceremony, Bush's only living daughter, Dorothy Bush Koch, read an adapted excerpt from William Shakespeare's Romeo and Juliet, the same lines recited by Robert F Kennedy at the Democratic National Convention in 1964, in a tribute to his slain brother, former president John F. Kennedy.

The passage reads, "and when she shall die, take her and cut her out in little stars, and she will make the face of heaven so fine, That all the world will be in love with night and  pay no worship to the garish sun”.