US Defence Secretary Robert Gates arrived in Indonesia Monday to discuss potential sales of military aircraft and deeper military ties, despite wariness on the part of both US lawmakers and Jakarta.

Gates is expected to press for expanded exchanges and training to solidify military ties that were renewed in 2005 after a 13-year break prompted by Indonesia's bloody crackdown on pro-independence protesters in East Timor.

The Pentagon is also interested in selling Indonesia more F-16 fighter aircraft, C-130 transport planes and helicopters as well as spare parts for its existing US-made aircraft, US defence officials said.

Gates was scheduled to meet with President Susilo Bambang Yudhoyono and Defence Minister Juwono Sudarsono, and to speak to the Indonesian Council on World Affairs during the one-day visit.

Senior US defence officials cite Indonesia's strategic importance in Southeast Asia and its political weight as the world's most populous Muslim state as key reasons for seeking closer military relations.

But the officials said that despite full normalisation in 2005, military relations are still restrained by "a perceptual lag" in the US Congress and among Indonesians as well.

The perception in Congress of the Indonesian military "is largely, although not entirely, of the pre-reform Indonesian military. They don't really appreciate how much progress they've made," one official said.

Vetting of the human rights records of Indonesian military officers going to the United States for military training, as required under US law, has been one irritant, the official said.

US lawmakers, or their staff, "are always trying to put limits on the areas in which we can engage the Indonesians on," the official said.

US officials argue that the Indonesian military is undergoing major reforms, pulling back from involvement in politics and moving to a more transparent budget instead of relying on military enterprises as a source of off-line revenues.

The Indonesians, on the other hand, "are suspicious also that we're the old United States, ready to pull the plug on them," the official said.

"The secretary is ideally situated in this trip to dispel the Indonesian perception gap, while pushing forward on the real engagement part," he said.