Mario Andretti believes Ferrari are capable of winning every race, starting with this weekend's Monaco Grand Prix, after a fine re-establishment of their Formula One title credentials.

Sebastian Vettel leads the drivers' standings by six points from Lewis Hamilton after five races of 2017, while Ferrari are trailing Mercedes by just eight in the constructors' race.

Vettel has won in Australia and Bahrain, with Hamilton closing the gap at a flawless Spanish Grand Prix for the Silver Arrows star last time out.

Monaco looms this weekend, with Ferrari red absent from the top step of the podium since Michael Schumacher's victory way back in 2001.

But Andretti, 1978 world champion and a former Ferrari driver, says the team's newfound pace and desire to win could make the difference.

Andretti told Omnisport: "I know Ferrari in the last two or three years hasn't been competitive but especially for Monaco they will be up to it. 

"And to be honest this season Ferrari can win every race. 

"They proved they are absolutely competitive with Mercedes and as a Ferrari fan I hope for the best.

"Am I surprised to watch Ferrari being able to win? To be honest I am not as I know that no other team in the world can work as hard as Ferrari. 

"They never rest and now with this rivalry with Mercedes, Ferrari will push and push and keep pushing to get the result."

After four consecutive championship triumphs in a dominant Red Bull car between 2010 and 2013, Vettel's comeback to the title picture has been another high point for Ferrari.

The German has either won or come second in each race so far this year, but Andretti stopped short of branding him outright favourite for glory at the end of the season, owing to a crowded scene at the front of the grid.

"It's hard to consider Sebastian as favourite for the championship but he's certainly a protagonist," the American explained. "And if the situation remains the way it is, nobody can rest on anything.

"So I think again, Ferrari is continuing - everyone continues to work. But never short-change Ferrari as far as their effort, because they live, breathe, eat and sleep Formula One.

"We can only hope that there will be more of a challenge up there. 

"Historically you would like to think Red Bull has the next best chance to be a challenger and have a trio [of teams fighting at the front]. 

"Formula One historically has never really had more than three teams really competitive so I think Red Bull is another one but they have the capability and sooner or later you hear from them. Look at the talent they have as drivers, that's something Formula One can look forward to."