KUALA LUMPUR, Malaysia (AP) — The Association of Southeast Asian Nations welcomed East Timor as its newest member Sunday, which its prime minister said was a “dream realized” for the tiny nation, while Cambodia and Thailand signed an agreement expanding a ceasefire on their borders with the hope it will lead to a lasting peace.

“Today, history is made,” Prime Minister Xanana Gusmao told the other leaders as the flag of East Timor, also known as Timor Leste, was added to the other 10 on the stage at a formal ceremony in Kuala Lumpur.

It was ASEAN's first expansion since the 1990s and was more than a decade in the making.

“For the people of Timor Leste this is not only a dream realized, but a powerful affirmation of our journey — one marked by resilience, determination and hope,” he said.

The ceremony marked the opening of ASEAN's annual summit, followed by two days of high-level engagements with key partners including China, Japan, India, Australia, Russia, South Korea and the U.S.

Thailand and Cambodia sign expanded border ceasefire

Shortly after his arrival Sunday, U.S. President Donald Trump took part as Cambodia and Thailand signed a formal expansion of the ceasefire that he helped broker this summer to end their border conflict.

“There was a lot of killing. And then we got it stopped, very quickly,” Trump said before Cambodian Prime Minister Hun Manet and Thai Prime Minister Anutin Charnvirakul signed the agreement.

The terms of the agreement include Thailand releasing 18 Cambodian soldiers held prisoner and for both sides to begin removing heavy weapons from the border area.

There were few details in the agreement on how it would be carried out, though it said the leaders agreed to establish an observer team made up of ASEAN member states “with the objective of ensuring the full and effective implementation.”

Both Cambodian and Thai leaders called the agreement a “joint declaration” on the ceasefire, while Trump dubbed it the “Kuala Lumpur Peace Accords”

“This declaration, if fully implemented, will provide the building blocks for lasting peace,” Anutin said. “But more importantly, it will begin the process of mending our ties.”

Hun Manet said that "Today marks a historic moment of profound significance for Cambodia and Thailand — a day where we affirm our shared conviction that peace is always possible when nations have the courage and wisdom to pursue it together."

Trump said he was signing economic agreements with both of those nations and was also due to sign a trade deal with Malaysia later in the day.

Chinese Premier Li Qiang, Canadian Prime Minister Mark Carney and Japan’s newly inaugurated Prime Minister Sanae Takaichi are among more than a dozen other leaders expected to be on hand.

Membership in ASEAN could help the one of world's poorest countries grow

East Timor's accession to ASEAN gives the country, which has just 1.4 million people and a GDP of around $2 billion, better access to an economic community of nations with some 680 million people and a $3.8 trillion economy.

Malaysian Prime Minister Anwar Ibrahim, whose country holds the bloc's rotating chairmanship, said East Timor's accession “completes the ASEAN family, the affirming of our shared destiny and deep sense of regional kinship.”

He said ASEAN's goal was to “pursue growth that is both resilient and fair, and to safeguard the welfare of generations to come.”

The integration of the region’s youngest nation, and one of its poorest, demonstrates ASEAN's “inclusivity and adaptability, especially at a time of geopolitical flux,” said Angeline Tan, an analyst with Malaysia’s Institute of Strategic & International Studies:

"As protectionism is on the rise, the expansion of ASEAN demonstrates its commitment to regionalism, openness and equal participation,” she said.

The last country to join ASEAN was Cambodia in 1999.

East Timor, wedged between Indonesia and Australia, was a Portuguese colony for over four centuries before declaring independence in 1975.

Indonesia invaded nine days later, beginning a brutal 24-year occupation that claimed tens of thousands of lives through conflict, famine and disease. A U.N.-supervised referendum in 1999 paved the way for independence, which was formally restored in 2002.

Today it is led by two independence heroes, Prime Minister Gusmao and President Jose Ramos-Horta, who won the Nobel Peace Prize in 1996.

They are trying to tackle high levels of unemployment, malnutrition and poverty. Some 42% of the country's population live below the national poverty line. Nearly two-thirds of its citizens are under 30 years old, making youth job creation a high priority.

Its major source of government revenues comes from the oil and gas industry, but with resources quickly becoming depleted it is looking to diversify.

Initially, the idea of bringing East Timor into ASEAN was met with skepticism by several other members, and even though that was overcome, Joanne Lin, co-coordinator of the ISEAS–Yusof Ishak Institute’s ASEAN Studies Centre in Singapore, said adding the nation is “not without challenges.”

“Timor-Leste’s administrative and institutional capacity still lags behind most ASEAN members, and full participation will require sustained technical and financial support from the secretariat and member states,” she said. “But its inclusion also brings new energy and perspectives — especially on issues like youth empowerment, democratic governance and small-state diplomacy.”

For East Timor, ASEAN membership gives it access to the bloc’s free trade deals, investment opportunities and a broader regional market.

East Timor applied for membership in 2011 and was granted observer status in 2022.

“For us this new beginning brings immense opportunity in trade, investment, education and the digital economy — we are ready to learn, innovate and uphold good government,” Gusmao said.

“This is not the end of a journey, this is a beginning of an inspiring new chapter.”