Former UN ambassador Nikki Haley said on Tuesday that she will seek the Republican presidential nomination in 2024, putting her at odds with one-time boss Donald Trump, the ex-President also seeking to win back the White House.

“I’m Nikki Haley and I’m running for President,” Haley said in a video that her team sent out by email. Haley, a former South Carolina governor who served as US ambassador to the UN under Trump, will lay out her campaign plans in a speech in Charleston, South Carolina, on Wednesday. She became Trump’s first direct challenger in a Republican field expected to grow in coming weeks and months. Her announcement was a sign the Republican nomination race is picking up steam.

Other high-profile Republicans looking at a 2024 run include Florida governor Ron DeSantis, former vice-president Mike Pence, US senator Tim Scott of South Carolina, New Hampshire governor Chris Sununu and former Arkansas governor Asa Hutchinson, among others.

“It’s time for a new generation of leadership — to rediscover fiscal responsibility, secure our border, and strengthen our country, our pride and our purpose,” Haley, 51, said in her video. She also harked back to her foreign policy experience with a folksy flair. “China and Russia are on the march. They all think we can be bullied, kicked. You should know this about me: I don’t put up with bullies. And when you kick back, it hurts them more if you’re wearing heels,” she said.

Trump, 76, whose own campaign has got off to a slow start, on February 2 mocked Haley on his Truth Social platform, noting she had earlier said she would support Trump if he ran in 2024. “Nikki has to follow her heart, not her honour. She should definitely run!” he wrote. The daughter of two Indian immigrants who ran a successful clothing store in a rural part of the state, Haley has gained a reputation in the party as a solid conservative who has the ability to address issues of gender and race.