Brazil's interim government has agreed to provide the state of Rio de Janeiro with 850 million US dollars in emergency funds to guarantee security at this year's Olympic Games.

The cash will be sent in a lump sum after after a new credit line was "opened" in the federal government's budget, according to Brazil's official gazette.

The authorization was signed by acting President Michel Temer, justice minister Alexandre de Moraes and finance minister Henrique Meirelles.

Tuesday's announcement came four days after Rio's interim governor Francisco Dornelles issued a decree that said the debt-laden state faced a public calamity.

Falling tax revenue stemming from the state's worst financial crisis in decades meant public services faced "total collapse", Dornelles said.

Brazil plans to deploy around 85,000 soldiers and police during the Olympics, roughly double the number used at the London 2012 Games.

Earlier this year Rio's state government cut 550 million US dollars from its Olympic security budget, but denied the move posed a risk to safety.

The Rio 2016 Olympics will be held from August 5 to 21.