US secretary of state Hillary Clinton has praised Australia's efforts to maintain stability in the Asia-Pacific region as part of a forum in Melbourne.

Ms Clinton is speaking to a group of young Australians at a town-hall style event at Melbourne University, hosted by ABC1 Lateline's Leigh Sales and broadcast on the ABC.

She says she has been impressed with the way Australia has helped out its neighbours when problems have arisen.

"Australia has always understood and accepted this responsibility," she said.

"It has increased military cooperation with Malaysia and Singapore, provided crucial assistance in Timor Leste's transition to independence, and led stabilisation forces in the Solomon Islands."

Ms Clinton has also thanked Australia for its support in the aftermath of September 11 terrorist attacks.

She says the United States has no better friend than Australia.

"Americans will never forget that after the terrorist attacks of September 11, Australia invoked our treaty alliance," she said.

"That meant a great deal to us. And we grieved with you, after terrorist murdered 88 Australians in Bali. So the United States has no better friend than Australia."

Ms Clinton says she is seeing signs of progress in Afghanistan and has reaffirmed plans to draw down US troops next year.

She says people on the ground are telling her that international forces are having an impact despite the death toll.

After making her opening remarks, the secretary of state faced questions from the audience, who were chosen by the US state department.

She also responded to questions posted on the ABC News Facebook page and on Twitter with the hashtag #hillaryoz.

Asked about gay marriage, Ms Clinton stopped short of endorsing it, but said she supports civil partnerships for gay and lesbian Americans.

She says the issue of same sex marriage is best left to individual states.

"I have not supported same sex marriage," she said.

"I have supported civil partnerships and contractual relationships, yet I am supportive of our states taking actions that they believe reflects the evolution of attitudes about this."

Tomorrow Ms Clinton will take part in the annual Australia-US ministerial talks, where the war in Afghanistan and the rise of China will be prominent topics.