Nigerian Senate gives deadline for Sick Presidents.

Nigeria's Senate has voted to amend the constitution, setting a time limit for presidents to formally announce their inability to carry out their role.

If passed, the head of state would have 14 days to declare their absence in writing - then MPs would vote for the deputy to become acting president.

The move came after President Umaru Yar'Adua returned home after spending three months in a Saudi hospital.

His return has sparked a row over the vice-president's official role.

The amendment will need the approval of the legislatures in two-thirds of Nigeria's 36 states before becoming law.

On Mr Yar'Adua's return, the presidency said Goodluck Jonathan would continue to run state affairs while the president recuperated.

But Mr Jonathan's appointment by parliament as acting president during Mr Yar'Adua's absence was controversial and enters unchartered territory.

YAR'ADUA ILLNESS TIMELINE 23 Nov 2009: Goes to hospital in Saudi Arabia 26 Nov: Doctors say he has pericarditis, a heart problem 23 Dec: First court case filed urging him to step down 12 Jan: President gives telephone interview from Saudi Arabia 27 Jan: Cabinet declares president fit 9 Feb: Vice-President Goodluck Jonathan made acting president 24 Feb: Yar'Adua returns Profile: President Umaru Yar'Adua Q&A: Nigeria political crisis Suffering and cursing in Nigeria Yar'Adua returns: Your comments

When the president's allies formally announced Mr Yar'Adua's arrival home - they pointedly referred to Mr Jonathan as the "vice-president", appearing to strip him of this acting president role.

Then a group claiming to speak for Mr Jonathan hit back with a statement calling him "acting president" three times.

The BBC's Caroline Duffield in the capital, Abuja, says Nigerian politics is always murky - but that difference in title clearly matters.

And there are now few rules to guide what happens next, she says.

Mr Yar'Adua's condition is unknown and he has not been seen in public since 23 November.

"We do not think he has the capacity today. We are appealing to him, and his handlers, that he should honourably resign his appointment," Osita Okechukwu of the Conference of Nigeria Political Parties, a group representing opposition parties, told the BBC.

But our reporter says the president's tight-knit circle have bought him home for a reason.

Analysts say that the struggle for the leadership is really about money.

Whoever holds power also has access to a patronage machine - oiled by billions of dollars from the Niger Delta.

That is a prize that many people are willing to fight for, our correspondent says.