President Maithripala Sirisena has said the international community need not worry about matters of state interest and the investigation into war crime charges should be internal and indigenous, without violating the laws of the country.
“Foreign judges and prosecutors should not be involved in an investigation into allegations of war crimes. I believe in the judicial system and other relevant authorities in this regard,” he said.
In a BBC interview, President said the country did not need to "import" specialists.
The government previously backed a UN resolution calling for a war crimes court supported by foreign judges.
But on Thursday the president said: "I will never agree to international involvement in this matter."
"We have more than enough specialists, experts and knowledgeable people in our country to solve our internal issues," he said.
Asked when the special court might be set up, he said: "These things cannot be done instantly or in a hurried manner. We will certainly reach our target but it's a process."
President Sirisena said that while the UN report released in September 2015 had pointed to army involvement in war crimes, the report had failed to mention names.
He said it was important to determine whether such crimes actually took place.
"If the Army is alleged for such crimes, our concern should be to free them from those allegations. If anyone has committed a crime, there's no doubt that they should be punished. However it is wrong to make the entire army guilty for what happened," he said.
The president also dismissed reports from the advocacy group Freedom from Torture that people in detention were still being tortured.
Saying the claims were made by people who were close to the Tamil Tigers, President Sirisena added: "I totally deny that. If someone can prove with evidence, I am ready to give them the opportunity. Justice is served equally in this country."