Washington: The US Supreme Court has cleared the way for the Trump administration to tap billions of dollars in defence funds to build sections of a border wall with Mexico.

The court's five conservative justices gave the administration the green light to begin work on four contracts it has awarded using Defence Department money. Funding for the projects had been frozen by lower courts. The court's four liberal justices wouldn't have allowed construction to start.

US President Donald Trump visits a section of the border wall with Mexico in Calexico, California, in April. Credit:AP

The justices' decision to lift the freeze on the Pentagon money allows Trump to make progress on a major 2016 campaign promise heading into his race for a second term. Trump tweeted after the announcement: "Wow! Big VICTORY on the Wall. The United States Supreme Court overturns lower court injunction, allows Southern Border Wall to proceed. Big WIN for Border Security and the Rule of Law!"

A trial court initially froze the funds in May and an appeals court kept that freeze in place earlier this month. The freeze had prevented the government from tapping approximately $US2.5 billion ($3.6 billion) to replace existing sections of barrier in Arizona, California and New Mexico with more robust fencing.