Malaysia and Indonesia have struck a landmark deal to try to save the critically endangered Sumatran rhino, whose population stands at fewer than 100, the International Union for Conservation of Nature said Thursday.

The Swiss-based environmental body said the accord was reached at a summit of its species survival commission which it convened in Singapore.

The IUCN noted that it was the first time that Malaysia and Indonesia have joined forces to address the dire state of the species, of which the last wild populations are believed to survive in Sumatra, western Indonesia and Sabah, Malaysia.

"Serious steps must be taken to roll back the tide of extinction of the Sumatran rhino," Widodo Ramano, head of the Rhino Foundation of Indonesia, was quoted as saying by the IUCN.

"This could be our last opportunity to save this species and, by working together as a collaborative unit, internationally and regionally, with an agreed vision and goals, a glimmer of hope has been clearly demonstrated," he added.

Laurentius Ambu, of the Sabah Wildlife Department in Malaysia, said the plan could involve steps such as exchanging reproductive cells of the species and moving individual rhinos between the two countries.

The two governments now need to formalise their collaboration and agree on steps to tackle the Sumatran rhino crisis, with experts at the summit proposing a two-year emergency plan to drive the process.

Mark Stanley Price, chairman of the IUCN's species conservation arm, said inter-governmental cooperation was crucial if the Sumatran rhino were to survive.

The Sumatran rhino is the only remaining two-horned rhino in Asia, a species that has lived on the planet for 20 million years.

It is one of the world's rarest rhino species.

Two rhino subspecies -- the Western Black rhino and one form of the Javan rhino -- have officially been declared extinct since 2010.