The Indonesian, Singapore and Malaysian navies began joint patrols of the vital Strait of Malacca shipping lane on Tuesday to combat piracy and terrorism and demonstrate they can handle the job.
One senior military officer, however, opened the door a crack for forces from other countries to play a role one day.
Seventeen vessels - seven from Indonesia and five each from Malaysia and Singapore - took part in the early morning exercises on calm seas under sunny skies.
About 50 officials from the three littoral states, including their military and naval chiefs, watched as ships fired flares and half a dozen parachutists dropped from a plane into the water to be picked up by a small boat in a simulated pirate chase.
"Now, there are many countries having interest in the security of the Strait of Malacca," Indonesia's top military commander, army General Endriartono Sutarto, told reporters on the KRI Tanjung Dalpele, a Korean-made warship that joined Indonesia's fleet last year.
"So, we are intensifying what we have already had before through year-long co-ordinated ... continuous patrols, although not every day, and all three won't be able to take part each time."
The narrow strait between Malaysia and Indonesia, with Singapore at its southern entrance, carries more than a quarter of world trade and almost all oil imports to Japan and China.
Piracy has plagued the strait for centuries, but has worsened in recent years and since the September 11 attacks on the United States in 2001 the prospect of terrorist strikes has emerged.
Recent suggestions by the United States that its forces play a more active role in strait security sparked opposition from Malaysia and Indonesia, whose officials said they could take care of the matter. Singapore seemed more open to the idea.
Since the issue emerged, the littoral states have moved to increase activities, with the coordinated patrols a key step.
However, Sutarto said the door was ajar for help by ships of other countries, apparently contradicting refusals by Indonesian and Malaysian officials who have said forces from outside the region were not needed although other aid would be considered.
"We lack ships so probably if they have ships, they can offer help to us. We lack detecting skills while they have such abilities, so they can complement us," Sutarto said.
Such help must first win approval from all three nations, he said.
The International Maritime Bureau recorded 445 pirate attacks last year, the second-highest since it began compiling data in 1992, and of those about one-third took place in Indonesian waters, including in the Malacca Strait.
More than 50,000 commercial vessels sail the 800-km (500-mile) channel each year.
Last month, regional naval chiefs agreed to create a task force made up of navies from each nation operating under their national commands. That side-stepped the issue of sovereignty that formerly slowed co-operation on Malacca Strait security.