Australia is keen to work with communications companies to crack encrypted messages used by terrorists, Foreign Minister Julie Bishop told a high-powered panel at the United Nations.

Bishop, speaking in New York on Wednesday at an event headed by British Prime Minister Theresa May, French President Emmanuel Macron, and Italian Prime Minister Paolo Gentiloni, congratulated Facebook, Microsoft, Twitter, Google, and YouTube for joining with governments to combat terrorists online.

While Australia supports an open, free, and secure internet, Bishop said encrypted messaging apps used by extremist groups are in the Australian government's sights.

"Australia is very keen to work constructively with communications service providers to prevent terrorists from using encryption to hide online," Bishop said.

"This is a significant challenge as encryption is vital for the protection of many legitimate activities including national security ecommerce and personal privacy.

"However, governments and the private sector have a shared interest and collective responsibility to combat the scourge of terrorism."

Bishop is heading Australia's delegation this week at the UN General Assembly, with Prime Minister Malcolm Turnbull choosing not to make the trip to New York.

She will hold a bilateral meeting with Microsoft co-founder Bill Gates later on Wednesday.

"We must do more in countering terrorists' exploitation of the internet," Bishop said.

"Australia supports an open, free, and secure internet; however, it cannot be an ungoverned space in which terrorists operate beyond the reach of the law."

A member of the Five Eyes intelligence agreement -- alongside the United States, the United Kingdom, Canada, and New Zealand -- Australia has been pushing the encryption issue among the group in recent months.

In June, Australian Attorney-General George Brandis said the issue is a priority for the government.

The push to deny encryption to a set of users on the internet is a bipartisan one in Australia, with the opposition Labor party signalling it will back any legislation.

"With terrorism a 21st Century conflict, we need 21st Century weapons to deal with it," Labor leader Bill Shorten said in July.

"The big tech giants have a position of privilege in our society, so it is appropriate that they contribute to the safety and well being of Australian society."

The Australian government has yet to publicly disclose how its plans would be implemented, but Turnbull has repeatedly stated that the government is not interested in the use of backdoors -- although it has been pushing an incorrect definition of backdoor.

"A backdoor is typically a flaw in a software program that perhaps the -- you know, the developer of the software program is not aware of and that somebody who knows about it can exploit," Turnbull said in July. "And, you know, if there are flaws in software programs, obviously, that's why you get updates on your phone and your computer all the time."

At the same press conference, Turnbull said the laws of Australia would trump the laws of mathematics.

"The laws of Australia prevail in Australia, I can assure you of that," he said. "The laws of mathematics are very commendable, but the only law that applies in Australia is the law of Australia."

With AAP