Ban on Thursday congratulated President Maithripala Sirisena, the government and people on the first year of the country's political transition, Xinhua cited a statement from the UN chief's spokesperson as saying.
Sri Lanka's reform agenda "aims to realize durable peace, stability and prosperity for the Sri Lankan people," said the statement.
The UN chief supports the Sri Lankan government's efforts to achieve a long-term political settlement acceptable to all, and welcomes its announcement to begin constitutional reform, it added.
"He calls on all stakeholders to cooperate in a spirit of inclusion and good faith," said the statement.
Sirisena, who assumed presidency a year ago, has vowed to set up a domestic mechanism to probe war crimes allegedly committed during the final stages of the country's civil conflict.
The Sri Lankan government on Thursday said it will begin a domestic accountability process next week.
The government will also release land to resettle displaced families who now live in refugee camps, said Rajitha Senaratne, a minister and spokesman for the cabinet.
Sri Lanka's civil war between government troops and Tamil Tiger rebels ended in May 2009 with the defeat of the rebels.
According to the UN, at least 40,000 Tamil civilians were killed during the conflict.