Federal Communications Commission Chairman Julius Genachowski will announce today that he will step down, according to an FCC official, leaving the agency after a four-year term that focused heavily on improving Internet access across the country.

Genachowski told FCC staff yesterday of his plans to make the announcement, the official and an industry source said. He has been widely expected to exit in coming weeks. His term expires in June.

A spokesman in Genachowski’s office declined to comment. Rules governing FCC appointments mean President Obama will nominate a new Republican commissioner and a Democratic chair in coming days.

Several people are considered likely candidates to head the FCC, including Tom Wheeler, venture capitalist and an Obama ally and fundraiser who is a known figure in Washington telecom circles thanks to his lobbying history at the National Cable Television Association and the wireless industry group CTIA.