Washington: US President Donald Trump addressed through video thousands of anti-abortion activists gathered in Washington to take part in the 45th annual March for Life.

Trump spoke from the White House Rose Garden on Friday and marchers watched on giant screens set up on the National Mall.

"We are protecting the sanctity of life and the family as the foundation of our society," Efe quoted Trump as saying.

During his first week in office, Trump signed an executive order prohibiting US government funding for foreign organisations that even provide abortion counselling, a decades-old Republican policy overturned by President Barack Obama in 2009.

Earlier this week, the president announced the creation of a new division within the Department of Health and Human Services to extend legal protection to health care workers who cite religious grounds in refusing to perform abortions or provide treatment to transgender patients.

"Under my administration, we will always defend the very first right in the Declaration of Independence and that is the right to life," Trump told the activists.

Though Ronald Reagan and George W. Bush addressed the March for Life by telephone, Trump is the first president to do so using a video link.