(CNN) Sen. Kamala Harris rebuked President Donald Trump's leadership style and abrupt decision-making process Monday, noting that if she were to replace him in the White House she would not conduct foreign policy by tweet.

When asked about how she would have handled the civil war in Syria differently than Trump -- who suddenly announced he was withdrawing US troops from the war-torn Middle Eastern nation last month -- the California Democrat did not take issue with the substance of Trump's position but rejected his style.

"My concern is that we cannot conduct our foreign policy through tweets," Harris said during her first press conference as a presidential candidate.

Harris formally announced her candidacy for president Monday morning in a video released to social media. She's the latest candidate in a growing field of Democrats vying for their party's nomination in 2020, including three other women -- Sen. Elizabeth Warren, Sen. Kirsten Gillibrand and Rep. Tulsi Gabbard. Harris' candidacy was long-expected as she released a new book earlier this month and went on a book tour that served as a soft-launch for her presidential bid.

Harris, who visited a Syrian refugee camp in Jordan in April 2017, said she was concerned about human rights abuses in that country.

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