Secretary-General Ban Ki-moon is sending his political chief to Sri Lanka to press the government to step up the release of nearly 300,000 Tamil civilians who have been detained since the South Asian island's civil war ended in May.

Undersecretary-General for Political Affairs B. Lynn Pascoe said he will also press the government to keep its pledges to Ban to promote political reconciliation with the minority Tamils.

He will also ask Sri Lanka to tackle human rights issues, including establishing a body to determine accountability for abuses during the 25-year civil war.

Pascoe told reporters that Ban decided to send him to Colombo after he spoke to Sri Lankan President Mahinda Rajapaksa on Monday. He said he will leave Tuesday and return over the weekend.