Donald Trump will become the first American president to attend the annual "March for Life" event in Washington today, confirming his explicit support for the anti-abortion movement while celebrating significant legislative gains.

Thousands of protesters from all over the country are expected to gather in the capital to participate in the event, which has been organized since 1973 after the US Supreme Court recognized women's constitutional right to abortion.

"I see you on Friday ... O big crowd!" Trump wrote on Twitter on Tuesday in response to a Tweet from "March for Life" to promote the event.

As the 2020 presidential campaign season grows, abortion remains one of the most divisive issues in the United States. Opponents rely on religious beliefs to justify their position, while abortion rights activists say the procedure is guaranteed by a constitutional guarantee that gives women control over their bodies and their futures.

And 58 percent of American adults said abortion should be legal in most or all cases, according to a Reuters-Ipsos survey last year.

Despite this, anti-abortion achieved significant legislative gains in 2019. The Gutmacher Institute said 25 bans on various types of abortions had gained the force of law although many of them did not go into effect due to existing legal challenges.