The Australian government's commitment comes amid strengthening political opposition to the programme, which Hill defended in remarks to reporters Tuesday at the United Nations headquarters in New York.

"From an Australian perspective, we're looking well into the future," he said. "We don't have any threat against us from ballistic missiles at this time, but the day might come when we have."

Hill is to sign a memorandum of understanding that will commit Australia to working with its close ally on the programme, including assistance with research, over a 25-year period.

Critics have charged that the US programme is the next version of former US president Ronald Reagan's failed "Star Wars" missile defence shield, but Hill cautioned against understating the programme's possibilities.

"The new technologies have meant that there is the potential to protect against incoming ballistic missiles, and in the past that hasn't been possible. So why not take advantage of that?" he said.

"We will identify what's of particular interest to us, and where we can make a contribution, where our defence industry might be able to provide value."

Australia's opposition Labor party has said it fears the programme might prompt an arms race by China and India.

WAR.WIRE