Veteran US senator Orrin Hatch dies at 88

His death on Saturday was announced in a statement from his foundation, which did not specify a cause.

A staunch conservative on most economic and social issues, Hatch also teamed with Democrats several times during his long career on issues ranging from stem-cell research to rights for people with disabilities to expanding children's health insurance.

He also formed friendships across the aisle, particularly with the late Democratic senator Edward Kennedy.

Hatch also championed issues such as abortion limits and helped shape the US Supreme Court, including defending Justice Clarence Thomas against sexual harassment allegations during confirmation hearings.

He later became an ally of Republican president Donald Trump, using his role as chairman of the powerful Senate Finance Committee to get a major rewrite of the US tax codes to the president's desk.

Hatch retired in 2019. Trump had encouraged him to run again, but the longtime senator would have faced a tough primary battle and had promised to retire. Hatch instead stepped aside and encouraged Republican Mitt Romney, a critic of the former president, to run to replace him.

"Few men have made their mark on the Senate as he did," Romney wrote in a tribute to his friend and predecessor, praising his "vision and legislative accomplishment".

Utah senator Mike Lee called Hatch "a friend, a mentor and an example to me and countless others".

Senate minority leader Mitch McConnell, a Republican from Kentucky, praised Hatch's legislative acumen.

"Orrin's decades of leadership drove an unending catalogue of major legislative accomplishments and landmark confirmations," McConnell said.

Hatch was also noted for his side career as a singer and recording artist of music with themes of his religious faith, the Church of Jesus Christ of Latter-day Saints.

He is survived by his wife, Elaine, and their six children.

Hatch came to the Senate after a 1976 election win and went onto become the longest-serving senator in Utah history, winning a seventh term in 2012.

He became the Senate president pro tempore in 2015 when Republicans took control of the Senate. The position made him third in the line of presidential succession behind then-vice president Joe Biden and the Speaker of the House. His tenure places him as the longest GOP senator, behind several Democrats.

One issue Hatch returned to over the course of his career was limiting or outlawing abortion. He was the author of a variety of "Hatch amendments" to the Constitution aimed at diminishing the availability of abortions.

While unquestionably conservative, there were times Hatch differed from many of his conservative colleagues, including then-president George W Bush, when Hatch pushed for federal funding of embryonic stem-cell research.

In 1997, Hatch joined Kennedy in sponsoring a $US24 billion program for states to provide health insurance to the children of low-income parents who don't qualify for Medicaid.

Hatch also helped usher through legislation toughening child pornography laws and making illegally downloading music a prosecutable crime.

In 2000, Hatch sought the Republican nomination for president, saying he had more experience in Washington than his opponents and that he could work with Democrats. He withdrew from the race after only winning 1 per cent of the vote in the Iowa caucuses and then endorsed George W Bush.

He became a strong opponent of President Barack Obama's 2009 health-care law after pulling out of early bipartisan talks on the legislation. At one point, he said of the legislation: "It is 2074 pages long. It is enough to make you barf."

Hatch was used to playing tough - he learned to box as a child in Pittsburgh to fend off the attacks of older, larger students. Unafraid to fight, he said he always made a point to quickly become friends with those he had arguments with.

When Hatch announced he would not seek re-election in 2018, he said: "Every good fighter knows when to hang up the gloves."

Australian Associated Press