Browne, talking ahead of a meeting of the 25 EU defence ministers, offered his condolences to the families and colleagues of four British troops killed in an attack in Basra City, southern Iraq.
"Consistently we have said Iran and Syria must face their responsibilities," Browne said in Brussels.
"Iraq must be seen in the context of the region. We have been calling on Iran and Syria to engage with the new Iraqi government and accept their responsibility for peace," he added.
British Prime Minister Tony Blair was set to echo the call for greater involvement by Syria and Iran in efforts to secure peace in Iraq and the Middle East, during a keynote address in central London.
According to his office, he will restate his conviction that engaging Damascus and Tehran is crucial to end the mounting sectarian conflict in Iraq and get the deadlocked peace process in the wider region back on track.
He will "make clear to Syria and Iran the basis on which they can help the peaceful development of the Middle East rather than hinder it; and the consequences of not doing so", an aide said.
On Iraq, British newspapers on Monday reported that he will concede that Britain's approach must "evolve" to meet the changing nature of the conflict, amid mounting violence, including against US and British troops.

Copyright AFP (Agence France-Presse), 2006