The acting United States ambassador has praised former prime minister John Howard for tightening Australia's gun laws, and pointed out their effectiveness in reducing mass shootings, in the wake of Monday night's carnage in Las Vegas.

Speaking in Sydney on Tuesday morning, Charges d'affaires Jim Carouso said the murder of at least 59 people – the US's worst mass shooting – would kickstart another round of debate about US firearm control but pointedly drew a contrast with Australia's success in stopping gun violence.

Police officers tell people to take cover near the scene of a shooting near the Mandalay Bay resort and casino on the Las Vegas Strip. Credit:AP

"When Prime Minister Howard after the Port Arthur massacre made the political decision that this must not stand, he took incredible flak. He had to wear body armour is my understanding, for months after that. But he carried it through," Mr Carouso said.

He said the US was "still having that debate", including about the meaning of the Second Amendment, which protects the right to keep and bear arms but dates back to 1791 and is premised on the fact that a "well-regulated militia" is needed to secure a free state.