By Gray Phombeah BBC, Nairobi

Kenya's ruling party Kanu has suffered another blow in the run-up to the December general elections after another minister announced he was quitting the government and the party.

The resignation of Joseph Nyagah, a minister in the office of the president, comes several weeks after the issue of President Moi's successor split the party down the middle and led to the resignation and defection of key Kanu and government officials to the main opposition alliance.

I have accepted my constituents' demand and as of today have withdrawn from Kanu

Joseph Nyagah Former minister

The National Rainbow Coalition has come up with a sole candidate - former Vice President Mwai Kibaki - while Kanu has nominated Uhuru Kenyatta, Mr Moi's preferred candidate and the son of Kenya's first president.

Mr Moi, 78, is constitutionally bound to retire at next month's polls.

"I have accepted my constituents' demand and as of today have withdrawn from Kanu," Mr Nyagah told a news conference in Nairobi.

Options open

Mr Nyagah's resignation comes only a day after he presented his nomination papers to the ruling party's headquarters to defend his Gachoka parliamentary seat in central Kenya.

He did not disclose which party he will join - but it had been rumoured all day that he had privately indicated that he would be joining the main opposition alliance.

Veteran Mwai Kibaki leads the main opposition alliance

"My options are open and I will let you know where I will go," he said in response to a question on whether he too would join the opposition.

Mr Nyagah is expected to join a string of ministers who had resigned from the Moi government and defected to the opposition ahead of the December elections.

The dispute over President's Moi's choice of successor has torn apart his party which has ruled since independence in 1963.

The opposition National Rainbow Coalition now stand a good chance of breaking Kanu's unbroken 40-year grip on power.