Nigeria's cabinet has officially declared ailing President Umaru Yar'Adua fit enough to stay in office despite being abroad for more than two months for treatment.

The country's Senate is urging Mr Yar'Adua to pull back from the brink of a constitutional crisis by taking steps to transfer power to Vice President Goodluck Jonathan.

The president's prolonged absence from Nigeria has raised fears of a power vacuum and the 109-member-stong Senate voted unanimously to back the demand to formally notify the National Assembly of Mr Yar'Adua's "medical vacation". Without formal notification, the president cannot legally transfer power to his deputy.

Opponents say that failure to officially inform the Senate constitutes a breach of the constitution and argue that government ministers are acting out of self-interest, fearing for a cabinet reshuffle if Mr Jonathan were to become president.

Last week, a high court order gave cabinet ministers two weeks to decide if Mr Yar'Adua was still fit enough to rule the country. In a terse response, the cabinet said medical treatment outside the country "does not constitute incapacity to warrant…the removal of the president from office".

The president has not been seen in public since last November when he flew to Saudi Arabia for medical care.

Photo of President Yar'Adua in 2008 by World Economic Forum (Flickr)