Lieutenant General John Frewen, who is heading the Australian Defence Force's COVID-19 task force, says 100 troops were put on standby in larger states and territories after the prime minister said they would be available for help.

Smaller states and territories had 50 troops on standby after the March 27 announcement, which was aimed at the hotel quarantine program.

NSW and Queensland took up the support within days, Lt Gen Frewen told a Senate inquiry on Tuesday.

In mid-June Emergency Management Victoria Commissioner Andrew Crisp made a request for 850 troops but he withdrew it the next day.

"We received the request and then we received the cancellation of the request that cited change in operational and resourcing requirements," Lt Gen Frewen said.

"I've not had any conversations with the Victorian government about that (cancellation) request."

Lt Gen Frewen said 14 requests for support have come from Victoria, with 11 accepted, two withdrawn and one knocked back.

Victorian Premier Daniel Andrews told an inquiry last week the Australian Defence Force never offered to guard quarantine hotels but the defence minister claimed offers of support were extended to Victoria multiple times.

The botched program, which used private security companies, was the catalyst for Victoria's second coronavirus wave.

Mr Crisp said he did not ask for ADF help and it was not offered for hotel quarantine in March, adding it also wasn't discussed in April.

Troops have been at four aged care homes in Victoria and are currently helping with two.

Each has six ADF personnel.

More than 3000 troops are providing support around the country, with about half in Victoria.

The current agreement for assistance is due to finish at the end of September.

Australian Associated Press