WASHINGTON, United States (AFP) — Jeb Bush appeared all but certain yesterday to launch his White House bid on June 15, as fellow Republican and former Texas governor Rick Perry plunged once again into a crowded presidential pool.

“Hope you all will join me for a special day,” Bush, the son and brother of two US presidents, posted on Twitter, with a graphic showing the date 6.15.15.

The 62-year-old will make his much-anticipated announcement at Miami-Dade College’s Kendall campus, following a trip next week to Germany, Poland and Estonia.

He also tweeted his message in Spanish, a reminder that Bush is fluent in the language of his Mexican-born wife and of millions of Hispanic American voters.

Bush, a former two-term Florida governor who has amassed a substantial war chest in the months since expressing interest in following father George H W Bush and brother George W Bush into the White House, would enter an increasingly packed GOP field.

Perry, who kicked off his second presidential bid in four years yesterday by attacking “the arrogance of Washington”, is the 10th Republican to formally enter the 2016 race.

He joins the likes of US Senators Ted Cruz, Rand Paul and Marco Rubio, and former Hewlett-Packard boss Carly Fiorina.

Hillary Clinton is the front-runner on the Democratic side, with no current close competition.

The Republican field is more wide open, with some 16 possible major candidates. Five are bunched at the top of a recent Quinnipiac University poll with 10 per cent support each, including Bush and conservative Wisconsin Governor Scott Walker, who has yet to announce his candidacy.

Bush’s entry would place him in the top tier, even though he has experienced difficulty wooing evangelical voters who are important in early primary contests, and has struggled to answer questions over how his policies would differ from his brother’s, notably on Iraq.

After giving several confused answers he has now said he would not have invaded Iraq as his brother had in 2003, given what Americans know now.

The blunder raised concerns about Bush, who has not run for public office since 2002, as a candidate potentially ill-prepared to handle the fast-moving news cycles of the digital age.

Bush has insisted “I am my own man,” and stressed that brother George would not be a problem for his campaign.

“I seek out his advice. I love him dearly. I have learned from his successes and his mistakes,” Bush told CBS News on Sunday.

Bush has raised suspicion among core conservatives, particularly for supporting comprehensive immigration reform. He said Sunday he was “not going to back down” on the issue.

Yesterday the conservative Perry, 65, ditched his rebel-in-cowboy-boots look from his disastrous 2012 presidential bid in favour of a slick dark suit and his now-familiar bookish glasses, striking a tone alternating between optimism about America’s economy and worry about the state of the world.

“We have the power to make things new again, to project America’s strength again and to get our economy going again. And that is exactly why today I am running for the presidency of the United States of America,” he told a crowd in an aeroplane hanger near Dallas, Texas.

He slammed President Barack Obama’s two terms as “an era of failed leadership”, saying the commander in chief’s gravest mistake was pulling US troops out of Iraq.

He issued grave warnings about a duplicitous Iran and Obama’s negotiations with the Islamic republic to rein in its nuclear programme.

“My very first act as president will be to rescind any agreement with Iran that legitimises their quest to get a nuclear weapon,” Perry said.

He also talked up his 15-year experience running Texas, insisting he was tested in leading “the world’s 12th largest economy”.

“Leadership is not a speech on the Senate floor,” he sniped, in a dig at several of his nomination rivals.

“And we will not find the kind of leadership needed to revitalise the country by looking to the political class in Washington.”

Perry, the longest-serving governor in Texas history, was mocked in 2012 for what became known as his “oops” moment, when he forgot one of the three government agencies he promised to eliminate if he became president.