Foreign Minister Julie Bishop says last week's chemical weapons attack has "hardened" Australia's view that Bashar al-Assad cannot be part of the long-term solution in war-torn Syria.

Ms Bishop has also warned the government is concerned about the threat of terrorist attacks targeting Easter celebrations, in the wake of the bombings on Coptic Christian churches in Egypt on Palm Sunday. Islamic State claimed responsibly for the attacks, which have so far killed 43 people.

After maintaining for years that Mr Assad should be phased out of power once Syria is stabilised, the Turnbull government has joined the United States in turning up the heat on the regime and its global backer Russia, following last week's chemical weapons attack. Australia and other allies have expressed support for the Trump administration's surprise response, a missile strike against a Syrian military airbase said to be involved in the attack.

"Our position has always been that Assad has no long-term position as leader but when Russia came in and backed Syria, we needed to work with Russia and Iran and others who are supporting the Assad regime to transition him out of the leadership," Ms Bishop told Sky News on Monday morning.