"I have no intention of withdrawing the army from the north. As president, national security will be my responsibility," Sirisena told reporters.
He said he would not allow the country to be divided or allow the LTTE to regroup in Sri Lanka.
"We have not signed any agreement with the Tamil National Alliance or Sri Lanka Muslim Congress to devolve powers or divide the country," he added.
Sirisena has been accused of pledging to create a separate Muslim administrative enclave in the east to win SLMC support.
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He said that the political parties which are supporting him in the election have reached an agreement based on the 100-day election manifesto and nothing else.
The manifesto seeks to establish constitutional and electoral reforms rather than trying to address minority calls for political resolutions of issues concerning them, he said.
The TNA has maintained a demand for reduction of the Sinhala-dominated military from the Tamil north since the civil war with the LTTE ended in 2009.
Rajapaksa refused to deescalate the military presence citing national security considerations.
The US and western nations have also backed the TNA demand for reduced military presence in the former conflict zone in order to set up an active civil administration.
A team of observers from the Asian Association of Election Authorities (AAEA) and the Commonwealth Secretariat are here.
Bharrat Jagdeo, the chair of the Commonwealth observers said that concerns were also raised on possible poll fraud.
On the concerns of the use of the military on or before election day, Jagdeo said that the Commonwealth observers will meet the army to discuss the concerns if necessary.
The opposition leaders alleged last week that the military may force a vote boycott of the Tamils.
This is expected to help the incumbent as Tamils are expected in large numbers to favour Sirisena.