SYDNEY (AP) — In their first joint appearance abroad, U.S. Defense Secretary Jim Mattis and U.S. Secretary of State Rex Tillerson on Monday pledged unity with longtime ally Australia in fighting Islamic extremists who seek to intimidate the West.

"We are united, as I said, in our resolve, even against an enemy that thinks by hurting us they can scare us," Mattis said. "Well, we don't scare."

Mattis and Tillerson spoke alongside their Australian counterparts at the opening of a joint meeting expected to touch on a range of subjects including defeating the Islamic State, stabilizing Afghanistan and dealing with North Korea's nuclear threats. They planned to hold a joint press conference later.

Tillerson stressed the enduring U.S.-Australian alliance and said it will prevail in "this common fight we share against the most heinous of actions we've seen most recently in London yet again." He did not elaborate on the London attack.

Police say three men drove a van over London Bridge on Saturday and struck pedestrians before crashing the vehicle outside a pub. The attackers, wielding blades and knives, ran to a well-known fruit and vegetable market and there they stabbed people in several different restaurants. Seven people were killed and at least 48 were hospitalized. Police fired 50 bullets to stop the violence, killing the three attackers and wounding one member of the public.

In her opening remarks, Australian Foreign Minister Julie Bishop said "countering terrorism" would be high on the meeting's agenda.

"The global terrorist threat is ever evolving, we've seen brutal attacks in a number of European cities, we've thwarted attacks here in Australia, and so we want to discuss with you, the links back into the Middle East, the role we're playing with you in Iraq and Syria and also Afghanistan," Bishop said. "We are united in our resolve to defeat ISIS, the Islamic State terrorist organization and its ilk."

Australian Defense Minister Marise Payne said her government is concerned by IS linkages in Asia and the Pacific.

"For Australia, from our perspective today it's important that we do discuss ISIS's links in Southeast Asia, violent extremist organizations and the risk that returning foreign fighters who may endeavor to resume positions in their own countries might pose in this region," Payne said. "They'll come back with battlefield skills, they'll come back with hardened ideology, they'll come back angry, frustrated, and we need to be very aware of that."