Nigeria's Vice-President Goodluck Jonathan has become acting¹ president, after weeks of political uncertainty² over the absence of its ailing³ leader.

经历数周政治动荡与病重总统的缺位，尼日利亚副总统乔纳森已成为代理总统。

Parliament earlier voted to recognise Mr Jonathan as acting president, in place of（代替） President Umaru Yar'Adua.

Mr Yar'Adua has not been seen in public since going to Saudi Arabia in November to get treated for a heart condition.

His continued absence has sparked legal challenges, cabinet splits（劈叉，裂口） and mass street protests.

It has led to a freeze in government business and threatened progress made in combating unrest（不安，动荡） in the oil-rich Niger Delta⁴.

'Pray fervently⁵'

"I am fully⁶ aware of the responsibilities reposed⁷（寄托，休息） in me, and I want to reassure⁸ all Nigerians that this is a sacred trust, which I shall discharge to my fullest abilities," Mr Jonathan said in a televised address on Tuesday.

In a country with a history of military coups⁹（军事政变） , and amid fears another one was possible, he thanked the armed forces for "their loyalty¹⁰ and devotion to duty during this trying（难受的，费劲的） period".

Mr Jonathan said he would build on the amnesty（大赦，特赦） for Niger Delta militants¹¹ begun by Mr Yar'Adua.

Some militants in the region have threatened to break the amnesty, citing government delays in implementing¹² the programme.

He asked the country to pray for Mr Yar'Adua's recovery.

"The circumstances - in which I find myself assuming office today as acting president of our country - are uncommon¹³, sober（冷静的，清醒的） and reflective.

"More than ever therefore, I urge all Nigerians as a people who have faith in God to pray fervently（热诚地，诚心地） for the full recovery of our dear president, and his early return."

Mr Yar'Adua is said to be receiving treatment for an inflammation of the lining¹⁴（衬里，内层） around the heart and he has long suffered from kidney problems.

Earlier on Tuesday, both houses of Nigeria's National Assembly passed a motion for Mr Jonathan to take over as head of state until Mr Yar'Adua is able to resume the presidency¹⁵.

The BBC's Ahmed Idris in Abuja says the move among the political elite¹⁶ to back the vice-president is unprecedented¹⁷（空前的） .

The ruling party alternates（交替，轮流） leadership between north and south, and Mr Yar'Adua's northern backers wanted to keep his southern deputy out of office.

Executive power is transferred to the vice-president under Nigeria's constitution when the president formally informs parliament of his absence.

Mr Yar'Adua never did this, but senate leader David Mark said that an interview Mr Yar'Adua carried out with the BBC's Hausa service on 12 January had effectively provided the assembly with the notice it needed.

But some analysts¹⁸ have suggested that the assembly's motion is not legally binding¹⁹ and could face court challenges.

Observers say the move has also laid down a challenge to the presidency and the cabinet - due to meet on Wednesday - to accept the handover or risk inflaming²⁰（激怒，燃烧） public opinion.