A senior opposition¹ politician in Nigeria has begun legal action to try to force the country's sick president to step down on health grounds.

尼日利亚一位高级反对党政客开始采用合法手段试图迫使患病的总统下台。

President Umaru Yar'Adua: No sign of his return from Saudi Arabia

President Umaru Yar'Adua has been seriously ill in hospital in Saudi Arabia for a month.

Farouk Adamu Aliyu of the All Nigeria People's Party has asked the federal high court to rule whether the president has the capacity to govern.

Doctors say President Yar'Adua is suffering from acute pericarditis急性心包炎.

The condition is an inflammation发炎，炎症 of the lining² of the heart.

Mr Yar'Adua has not formally handed over power and as a result Nigeria is locked in a political impasse僵局，死路.

Wild rumours³

Now Mr Aliyu has launched his court bid in order to establish three points:
whether the president's 30-day absence amounts to相当于，总计为 incapacity
whether the Nigerian government has broken the law on the issue
whether Vice-President Goodluck Jonathan can lawfully⁴ take power

The BBC's Lagos correspondent says a ruling from the court would help bring clarity to the situation in which wild rumours have swept the country.

These rumours have included claims that the president is in a coma陷于昏迷, or that he has been struck dumb哑的，不说话的.

Ministers have said the president is responding to treatment and have asked Nigerians to pray for恳求，请求 his recovery.