But he has not asked for US help, saying it is up to Australia to take the lead in working towards security in the Asia-Pacific region.
After their 30-minute meeting at the Pentagon, Mr Rumsfeld refused to be drawn on possible US involvement.
"We did have a discussion about some of the situations in areas that are neighbouring Australia, and the PM brought me up to date as to what was taking place and what they were doing," Mr Rumsfeld said.
Earlier Mr Howard urged the United States to become more involved in international affairs, saying it is the only way to ensure world peace.
Mr Howard made the plea to US Secretary of State Condoleezza Rice during an official lunch at the State Department in Washington, a day after a private dinner with President George W Bush.
The prime minister has powered through a series of meetings with senior US officials, including Rice, Defence Secretary Donald Rumsfeld, Energy Secretary Sam Bodman and the new chairman of the Federal Reserve, Ben Bernanke.
Ms Rice opened the lunch for about 100 dignitaries, including former US ambassador Tom Schieffer and former Federal Reserve chairman Alan Greenspan, with a toast to Mr Howard, his wife Janette and their son Richard.
Describing them as "very, very good friends", Ms Rice said the Howards were honouring America with their presence.
She said that on her recent visit to Australia, she was able to witness the depth and breadth of the extraordinary relationship between the two countries.
She was able to thank the families of Australian soldiers who served side by side with Americans in Iraq and Afghanistan.
"But all the way back, of course, to world wars that we successfully fought in the defence of freedom I was able to say to them that any time the United States is on the frontline in the defence of freedom, Australia is by its side. For that we thank you," she said.
"I can't thank you enough for all that Australia does, Prime Minister and Mrs Howard, I'd like to raise a glass to this friendship, to this friendship based on shared sacrifice, ...this friendship based on an expectation of an even brighter future, given all that we've achieved in the past."
Mr Howard told the lunch that Australian and US forces first fought together in 1917, beginning a shared partnership in military conflict unbroken to this day.
"In every major conflict our two countries have been engaged together," he said.
But it was the shared commitment to democracy and freedom, rather than the military association that tied the countries together, he said.
He said the direction of America's power and purpose was vital to all the nations of the world.
"Australia is one of those countries which is in the forefront of those who urge greater rather than lesser United States involvement in the affairs of the world," Mr Howard said.
"The involvement of your country in our own region is critical to its stability. And the energy and the intellect that you have brought to the position and the example that you represent in so many ways is a source of enormous admiration in my country and a source for very great respect around the world."