President Donald Trump holds the state flag of Texas outside of the Annaville Fire House after attending a briefing on Hurricane Harvey in Corpus Christi, Texas on August 29, 2017.

Three Texas landowners and an environmental group filed the first lawsuit on Friday challenging U.S. President Donald Trump's national emergency declaration aimed at freeing up billions of dollars to build a wall along the U.S. border with Mexico, the consumer advocacy group Public Citizen said.

The lawsuit, brought in federal court in the District of Columbia, claims the south Texas landowners were told by the U.S. government that it would seek to build a border wall on their properties if money for the project were available in 2019, Public Citizen said in a statement.