US President Barack Obama talks with senior advisors Valerie Jarrett, David Axelrod (2ndR), and Director of Communications Dan Pfeiffer (R), in the Oval Office, in this White House handout photograph taken on May 21, 2010 and released on June 7, 2010. [Photo/Agencies]

WASHINGTON - US President Barack Obama's top two communications advisers plan to step down in the coming months, leaving a hole in his senior staff as the White House tries to keep attention on an ambitious agenda before the 2016 presidential campaign.

Dan Pfeiffer, a senior adviser and longtime member of Obama's inner circle, is stepping down in early March, and Jennifer Palmieri, the White House communications director, plans to leave later this spring.

The moves are the most significant shake-up of White House staff since the 2014 midterm election when Republicans gained control of the US Senate and strengthened their majority in the House of Representatives.

Obama rejected calls for a shake-up at the time, and has managed to seize the initiative in Washington with changes to US-Cuba policy and a rollout of middle-class-focused ideas in his State of the Union address last month.

The White House painted the upcoming departures as a chance to bring in new blood.

"While their departures are significant, there is indeed value in bringing in new, energized staff with fresh ideas and new perspectives," a White House official said.