Washington, May 5 (IANS): The former US presidents George H.W. Bush (1989-1993) and George W. Bush (2001-2009) has ruled out the possibility of supporting Donald Trump for the presidency of the US.

The two former presidents has planned to "stay silent" in the race to the White House, Efe news agency reported on Thursday.

"At the age of 91, President Bush is retired from politics", spokesman Jim McGrath said, although the nonagenarian recently endorsed his other son Jeb Bush.

Meanwhile, the personal assistant of former president Bush (son) Freddy Ford, on Wednesday said the former president "does not plan to participate in or comment on the presidential campaign".

The 2016 presidential race will be the first election cycle in which the Bushes are not involved in the Republican nomination since both left office.

In 1996, Bush (father) endorsed the campaign of Bob Dole, his longtime political rival, while in 2000 and 2004, he also campaigned for his son George W. Bush.

In 2008 and 2012, both Bushes supported Republican nominees US Senator John McCain and Mitt Romney, respectively.

The former governor of Florida Jeb Bush, supported by his father and brother, dropped out of the GOP presidential race in February.

In Trump's victory speech in Indiana, the tycoon asked his fellow Republicans to bring "unity": "We have to bring unity -- this (election) is so much easier if we have it."