U.S. President Donald Trump on Thursday signed an executive order aimed at strengthening the federal government’s cyber security and protecting the nation’s critical infrastructure from cyber attacks, a senior administration official told reporters on a call.

A copy of the signed order was not immediately available.

The order is Trump’s first significant action to address what he has called a top priority of his administration.

The long-delayed order comes after Trump nearly signed a cyber security measure just days into his presidency in January before it was pulled back to allow for more input from different federal agencies and consultation with experts.

It follows a presidential campaign dominated by running storylines related to cyber security, including the hacking and subsequent leaking of Democratic emails as part of what U.S. intelligence agencies determined was a wide-ranging operation intended to help Trump win the White House and denigrate his challenger, Democrat Hillary Clinton.

(Reporting by Dustin Volz; Editing by Chizu Nomiyama and Lisa Von Ahn)