East Timor's independence was a gift to the world because it showed conflict could be resolved through negotiation, United Nations Secretary-General Antonio Guterres said on Friday, the 25th anniversary of its vote to separate from Indonesia.

The milestone will be marked later on Friday with a minute's silence for those who died during the campaign for nationhood, a march through the seaside capital of Dili, and speeches by Prime Minister Xanana Gusmao and President Jose Ramos-Horta, two heroes of the independence movement.

"We can never forget the courage of the Timorese resistance. By people who risked everything to see independence realised," Guterres told the Timorese parliament in Dili on Friday morning, in remarks provided by the U.N.

"But if Timor-Leste received a lot from the U.N., the truth is that it also gave a lot to the U.N. and the world. The talks mediated by the U.N. showed the world that it is possible to resolve conflicts at the negotiating table..."

The nation has evolved from a host country for peacekeeping forces to one that contributes personnel to U.N. peacekeeping missions, as it is doing in South Sudan, he said.

The tiny-half island nation of East Timor, or Timor-Leste, officially gained independence in 2002 after a landmark ballot overseen by the U.N. in 1999. More than 78% of Timorese choose independence at the time.

Pro-Jakarta militiamen went on a violent rampage following the 1999 vote, destroying infrastructure and killing about 1,000 people, according to the U.N.

Neighbouring Indonesia had invaded East Timor in 1975, occupying the country for more than two decades. Prior to the Indonesian occupation, the nation was ruled by colonial power Portugal.

Xanana, who served as East Timor's first president after independence, led resistance against the brutal occupation and was imprisoned by Indonesia after he was captured in 1992.

Ramos-Horta, the country's de-facto foreign minister in exile, was jointly awarded the 1996 Nobel Peace Prize for his efforts to secure his country's independence.

"My presence in Timor-Leste, at the moment the country became independent, was undoubtedly one of the greatest privileges that my political life has given me," said Guterres, who was Prime Minister of Portugal from 1995 to 2002.

"That day, and today, I felt the enormous courage and relentless determination of the Timorese people."

A quarter of a century after it gained freedom, the nation of 1.3 million faces significant development hurdles as it works to diversify an oil-and-gas-dependent economy, and foster a new generation of leaders.