Republican US senator Ted Cruz has confirmed he will run for president in 2016, the first major candidate to officially declare a bid in the next race for the White House.
"I'm running for president and I hope to earn your support!" the right-wing Texas conservative said on Twitter.
The 44-year-old grassroots Tea Party supporter has been senator in Texas since 2012, and is a long-time critic of Barack Obama's administration.
He has raised hackles in his own party in recent years when he helped push the US government into shutdown over budget fights, and for opposing Republican leaders on a series of issues.
In a 30-second video posted on Twitter on Monday, Cruz said it was time to "restore" America, and called on young conservatives to support him.
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"It's a time for truth, a time to rise to the challenge, just as Americans have always done," he said in the video.
"I believe in America and her people, and I believe we can stand up and restore our promise.
"It's going to take a new generation of courageous conservatives to make America great again and I'm ready to stand with you to lead the fight."
Cruz's advisers told US media he will aim to raise between $US40 million and $US50 million ($A51.39 million-$A64.24 million) for his campaign, and will rely on support from his Tea Party base.
Though the first to officially declare his presidential bid, other Republicans, including Jeb Bush, Wisconsin governor Scott Walker and senators Rand Paul and Marco Rubio have signalled they could join the race.
Democrat Hillary Clinton could be another presidential hopeful, and Cruz has said she "embodies the corruption of Washington."
