Texas senator Ted Cruz plans to announce tomorrow that he is running for US president.
The news comes from a strategist for the first-term Republican senator, who spoke to The Associated Press on condition of anonymity.
The 44-year-old will be the first high-profile candidate to formally launch a White House bid, although several Republican contenders are expected to enter the race in the coming weeks.
After joining the Senate in 2013, Mr Cruz established himself as an uncompromising conservative willing to take on Democrats and Republicans alike.
He promises to repeal President Barack Obama's healthcare law, abolish the tax-collecting Internal Revenue Service and scrap the Education Department.
As first out of the starting gate, Mr Cruz apparently hopes to get the jump on several top Republicans who are expected to enter the race in the coming weeks - former Florida governor Jeb Bush, Wisconsin governor Scott Walker and two Senate colleagues, Kentucky's Rand Paul and Florida's Marco Rubio.
Mr Cruz has considerable appeal among the Republican Party's base of conservative voters.
Criticised by members of his own party at times, he won praise from ultraconservative tea party activists for leading the Republican push to shut down the federal government during an unsuccessful bid to block funding for President Barack Obama's healthcare law.
That effort failed and cost Republicans support among the electorate in the short-term, but did not damage the party in the 2014 election when it expanded its majority in the House of Representatives and regained control of the Senate..
Mr Cruz is set to release a book this summer that he said would reflect themes of his White House campaign.
In a recent interview, he said he wants to counter the "caricatures" of the right as "stupid," ''evil" or "crazy".
"The image created in the mainstream media does not comply with the facts," he said.
The son of an American mother and Cuban-born father, Mr Cruz would be the nation's first Hispanic president. He was born in Canada but two lawyers who represented presidents from both parties at the Supreme Court recently wrote in the Harvard Law Review that Mr Cruz meets the constitutional requirement to run.
He has hinted openly at his intentions to seek the White House for months, and his intention to jump into the race was confirmed by a strategist.
Mr Cruz is scheduled to give the convocation at Liberty University in Virginia tomorrow. By selecting the school, a private Christian college founded by fundamentalist preacher Jerry Falwell, as the site for his announcement, Mr Cruz is also sending a clear signal to conservative Republican primary voters about his candidacy and his political positioning heading into the race.
He has assiduously courted evangelicals and other social conservatives as part of an attempt to build a coalition of conservatives frustrated with Republican Party elders in Washington.
One of the nation's top college debaters while a student at Princeton University, Mr Cruz continues to be a leading voice for repeal of the Affordable Care Act, widely known as Obamacare. He also promises to abolish the tax-collecting Internal Revenue Service, scrap the Education Department and curtail federal regulators, likening them to locusts.
He also is a staunch social conservative, who opposes both gay marriage and abortion rights. His father, Rafael, is an outspoken evangelical pastor.
On foreign policy, mr Cruz was among 47 Republican senators who signed a letter to Iran's supreme leader warning that any nuclear deal that is struck with the Obama administration and five other world powers could become null and void after the 2016 election when the current president leaves the White House. Mr Cruz is a strong backer of Israel.
He also is opposed to Mr Obama's executive action to ease deportations of millions of immigrants in the country illegally and the White House opening to communist Cuba, his father's homeland.
Mr Cruz has left little doubt about his 2016 intentions in recent weeks. He made his first trip to New Hampshire earlier this month to help lay the groundwork for a presidential campaign, having already begun to ramp up outreach to party activists and donors.
Tiny New Hampshire holds the first presidential primary vote and a victory there can give a candidate a strong push toward the party nomination.