The industrial action campaign, initially scheduled for the Easter weekend, was postponed by the Community and Public Sector Union after terror attacks in Brussels and the urging by Prime Minister Malcolm Turnbull.

The protected industrial action is set to last until April 7 with staff walking off the job during morning and evening peak times.

On Wednesday, union members at Sydney Airport will strike between 5am and 1pm and again between 4pm and midnight. On Thursday, staff at Melbourne Airport will strike between 4am and midday and again between 4pm and midnight.

CPSU national secretary Nadine Flood has warned travellers the strike action will likely result in delays for those travelling on international flights.

"Our members in Immigration and Border Force and Agriculture and Water Resources will now resume their industrial action, knowing that their campaign never has and never will compromise Australia's national security at airports or anywhere else," she said.

"These workers remain angry and frustrated at the way they've been treated by this government, with no-one listening to their concerns for their livelihoods and their families after two years of attacks on their rights and pay."

According to the CPSU, strict national security exemptions will remain in place at international airports during the strike action.

In the wake of the attacks in Brussels last week, Mr Turnbull "strongly encouraged" union members to rethink the industrial action and urged them "to pursue their complaints, their disagreements with the government through other means".

In a statement, Ms Flood said the Prime Minister needed to ensure the complaints of public servants were not ignored with many left angry and frustrated by the government's bargaining position.

"Giving someone the job of actually talking to us would be a start, given the government has refused to meet with us since October last year," she said.

"The government has an unworkable bargaining policy that holds these workers to ransom; sign up to give up your rights or go into the third year of a wage freeze.

"We want this to be resolved, and the sooner the better."

Department of Agriculture staff working in biosecurity will also join the rolling industrial action.

Last week, public service commissioner John Lloyd condemned proposed strike action at international airports as cynical and deliberately designed to cause maximum disruption.

Mr Turnbull said security at international airports would not have been undermined by the strike action as it was primarily the concern of the Australian Federal Police, rather than the Australian Border Force.

"I can assure you the AFP has that in hand and the AFP's security levels at the airport, the commitment of personnel, their operational awareness and so forth is consistent," he said.