The federal and state governments have been looking at changes to control orders for a considerable time, says Prime Minister Malcolm Turnbull.
Malcolm Turnbull says changes to anti-terrorism control orders are not a direct response to the October 2 shooting in Parramatta.
The government will bring to parliament in November new laws to lower the age at which terror suspects can be slapped with control orders to 14.
The prime minister on Tuesday said the law change had been in the works for "some considerable time", rather than a response to the execution-style shooting of police accountant Curtis Cheng outside the NSW police headquarters.
Attorney-General George Brandis has defended plans to reduce the age at which teenager terror suspects can be slapped with control orders.
The measure will be included in the fifth instalment of national security legislation, developed in consultation with the states, that will be introduced to parliament in November.
Some lawyers and a former reviewer of national security laws have questioned the flagged measures.
But Senator Brandis on Tuesday cited the recent shooting of NSW Police accountant Curtis Cheng by a 15-year-old boy in Sydney's west, saying it demonstrated 14 was not too young for an order to be made.
"Unfortunately the reach of ISIL and ISIL surrogates and agents in Australia is extending to younger and younger people," he told ABC radio.
The legislation will include safeguards limiting the capacity of police to question or deal with minors in ways regarded as "unreasonable".
Under existing federal laws, a terrorism suspect can be kept in custody for up to four hours before a court application needs to be made to extend the detention to up to eight days.
The NSW government wants suspects held for up to four days, with a court able to extend the period to 28 days.
The opposition is yet to be given details.
"Labor supports our police and security agencies having the powers they need to keep Australians safe," shadow attorney-general Mark Dreyfus told AAP.
"Labor has demonstrated our commitment to working constructively on matters of national security.
Former national security legislation watchdog Bret Walker said he doubted whether the measures were better than arresting suspects, charging them and then remanding them in custody.
"We do have to be careful about just laying layer after layer of law in relation to dealing with people who probably require to be surveilled, investigated and in appropriate cases charged," he told ABC radio.
Mr Walker also warned that anyone subject to a control order was likely to be very hostile towards authorities which could be counter-productive to any investigation.
The Australian Lawyers Alliance fears putting in place control orders to people as young as 14 could backfire.
"If you want to further radicalise people, if you want them feeling they are completely alienated from society and you do that to a 14 year old kid then you're going the right way about it," spokesman Greg Barns said.
Terrorism expert Greg Barton says extending control orders to keep suspects away from harmful elements and protect them could be useful as part of a larger package of measures.
"By itself though, it's not going to be a panacea," he said.
Security chiefs and government agencies are meeting in Canberra on Thursday to discuss ways to combat violent extremism.