Colombo, Dec 3 (IANS): Opposition presidential candidate Maithripala Sirisena kicked off his campaign Wednesday in the Sri Lankan capital, promising reforms as the countdown begins for elections in early January.

Sirisena reiterated his main election pledge of ending Sri Lanka's contentious executive presidency within 100 days if he is elected.

"We will form a national government. We will solve problems and assure democracy and rule of law," Xinhua quoted him as telling his supporters in Colombo.

The Jan 8 presidential election is expected to be a close run race with the opposition coalition gathering 10 crossovers from the government in the last few weeks.

Monday, Sirisena signed a memorandum of understanding (MoU) with 36 political parties and civil society organisations, including the main opposition, United National Party (UNP), to propel him to power.

"It is time for people to vote thinking of the country and its future," UNP leader Ranil Wickremesinghe said.

Sirisena was the secretary general of the ruling Sri Lanka Freedom Party (SLFP) and health minister before defecting to run against incumbent President Mahinda Rajapaksa, who is seeking an unprecedented third term in power.

He has pledged to end the executive presidency in 100 days should he be elected and put in place a national government composed of opposition parties.

Adding momentum to Sri Lanka's presidential race, the nationalist Jathika Hela Urumaya (JHU) Tuesday announced its backing for Sirisena.

The JHU, which is seen as having a strong pro-Sinhala Buddhist agenda, declared its support for Sirisena after President Rajapaksa's government declined a reform agenda proposed by the party.

The JHU has been highly critical of what it sees as the government's corruption and centralisation of power.

Rajapaksa is unlikely to be deterred from seeking re-election two years before his second term ends, analysts told Xinhua, adding Sirisena still needed to attract large-scale support to stand a chance of winning.