The acting president of Nigeria, Goodluck Jonathan, dissolved his Cabinet on Wednesday in the strongest assertion yet of his authority over a country where his rule has been challenged. The ministers were all inherited from Umaru Yar'Adua, the gravely ill president whose place Jonathan took in February. Analysts and presidential advisers suggested that they had become an impediment to Jonathan's attempts to put his stamp on the office. Information about Yar'Adua's condition has been sparse. Three weeks ago, he returned home after a long hospital stay in Saudi Arabia. Jonathan has had to deal with sectarian and ethnic violence in one region, a flare-up in the rebellion over oil in another and strife in the Cabinet. 'There are pro- and anti-Jonathan ministers in the Cabinet, and pro- and anti-Yar'Adua ministers, and they were polarized as to whether the acting president should act or not act,' said Hassan Tukur, a retired diplomat who is close to Jonathan. In a foretaste of Wednesday's dismissals, Jonathan dismissed Yar'Adua's national security adviser last week after mass killings near the city of Jos. 'It's the prerogative of the president to change the Cabinet whenever he feels the need to inject new blood, reinvigorate the Cabinet and give it a new focus, and that's what we've done here,' said Ima Niboro, Jonathan's spokesman. Others said that Jonathan's agenda was not helped by the infighting. 'There was a lack of cohesiveness in the Cabinet, and the Cabinet had become polarized, in a way that was harming effective governance on the core issues,' said a person close to the president who asked not to be identified because he was not authorized to speak to the press. 