The Trump administration has taken another step toward building a wall on the US border with Mexico, even as funding for the project remains in question.
US Customs and Border Protection (CBP) has announced it will award contracts to four companies to build four prototypes for the wall.
The CBP has provided few details of the concrete prototypes and said funding for four other prototypes for a see-through structure will be awarded next week.
The prototypes will cost a total of $3.6m.
Donald Trump made the construction of the wall his signature issue in last year's presidential campaign. He promised that Mexico would pay for it, but Mexico has refused.
The US president is now demanding that US Congress should fund the wall, and has threatened to shut the government if it does not do so.