Speaking at an election rally in Kurunegala on Thursday, Mr Wickremesinghe said if his party won the coming parliamentary polls, the country's national security would remain one if its main focus, reported Xinhua.
He said President Maithripala Sirisena would be the defence minister under a future United National Party (UNP) government.
Sri Lanka will face parliamentary elections on August 17 to form a new government.
The prime minister blamed former president Mahinda Rajapaksa for inciting racism, by claiming that his party had signed a secret pact with the Tamil National Alliance (TNA) to divide the country between the Tamils and the Sinhalese.
Mr Wickremesinghe's government has been criticised by the opposition on grounds that it had put national security at risk by dismantling some high security zones in the north and east, the former war zone.
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