The two strongest candidates in Uganda's general elections on Thursday have been holding their final rallies.
Mr Museveni has been credited with ending war in most of Uganda
President Yoweri Museveni warned that 12,000 army reservists had been called up to deal with any poll violence - seen as a warning to the opposition.
His main challenger Kizza Besigye is to address his supporters in the west.
These are Uganda's first multi-party elections for 25 years and Dr Besigye says the authorities have been trying to intimidate him and his supporters.
He has been arrested on charges of rape and treason. On Monday, his final campaign rally in the capital, Kampala, was cancelled after clashes between his supporters and police firing tear gas and water cannon.
Mr Museveni has been in power since 1986 and had been seen as one of a "new generation" of African leaders but has more recently been criticised for changing the constitution so he can contest the polls.
Chief UK election observer Chris Mullin has told the BBC that Dr Besigye's arrest showed the playing field was "not level".
Mr Museveni also blamed "foreign meddlers" for the recent spate of power cuts in Uganda.
He told some 20,000 supporters, mostly wearing the yellow of his National Resistance Movement, foreign donors had refused to fund new hydro-electric dams.
"Henceforth, we shall not listen to anybody when it comes to vital matters like defence, like energy, like roads, like politics," he said in Kampala.
Earlier, a US Christian evangelist, who the police say is linked to Dr Besigye, was arrested on firearms charges.
Police said two assault rifles were found at the Kampala home of Peter Waldron, 59.
Mr Mullin, a former UK Minister for Africa, told the BBC's World Today programme that there had only been "isolated" cases of violence during the campaign, despite Monday's clashes.
But he accused the ruling National Resistance Movement of conducting a "campaign of harassment" against Dr Besigye.
"There is no doubt the playing field is not level in terms of funding, or in terms of some of the restrictions placed on the opposition."
Lobby group Human Rights Watch has also said the polls would not be free and fair.
Electoral Commission chairman Badru Kiggundu on Tuesday asked election observers to "help us to learn. We are barely six months old in this multi-party democracy," reports Reuters news agency.
The government denies using the courts to block Dr Besigye and the police say they have proof that he was trying to work with rebel groups to unseat Mr Museveni.
On Monday, the president defended his record, saying Ugandans had enjoyed "core security" for 20 years despite problems in neighbouring countries.
Kizza Besigye says his supporters are being intimidated by the army
Mr Mullin also said that there is little doubt that most Ugandans are better off now than before Mr Museveni took power.
Last week, Dr Besigye urged his supporters to exercise restraint after two of his supporters were shot dead.
He alleged that the violence was part of a military campaign to intimidate his supporters.
Dr Besigye lost the 2001 elections to Mr Museveni and then went into exile, saying he feared for his life.
He returned last year and was arrested on charges of treason and rape.
Opinion polls suggest Mr Museveni is ahead of Dr Besigye but it is not clear if he will secure the 50% needed to avoid a second round.