BRISBANE, Australia, Feb 18 (Reuters) - The parents of an Australian journalist held on terrorism-related charges in Egypt have launched an online petition calling for his release days before his trial is due to start in Cairo.

Al Jazeera reporter Peter Greste has been charged, along with several colleagues, with publishing lies that harmed Egypt's national interest.

Greste's parents, Lois and Juris, have collected more than 30,000 signatures calling for Peter to be set free via their petition on campaign website avaaz.org.

"Hopefully by now people know a bit more about this story and will have more of an understanding of it and therefore when they see and hear about an Avaaz petition they are ready to actually help sign and help us," said Lois Greste at her home in Brisbane.

Greste and two colleagues were arrested at their Cairo hotel in December. The Al Jazeera staff are charged with helping a "terrorist organisation", an apparent reference to the Muslim Brotherhood, which has been protesting against the government since the army toppled Islamist President Mohamed Mursi in July.

The government has declared the Brotherhood a "terrorist group". The Brotherhood says it is a peaceful organisation.

Critics accuse the government of widespread human rights abuses and say it has undermined democratic gains made since a popular uprising toppled autocrat Hosni Mubarak in 2011. The government says it is committed to democracy.

"Peter is in no way a threat to anybody's safety or security, he is not a terrorism sympathiser, nor is he the bloke to falsify any news," his father, Juris, said.

If found guilty, Greste faces up to seven years in prison according to media reports.

"We just don't want to go near there. We cannot think that far ahead. Everything keeps changing almost from minute to minute in some respects and that's too far in the distance and it's too negative," Lois Greste said.

The trial is due to start on Thursday. (Reporting by Stuart McDill; Editing by Nick Macfie)