BRUEIL-CERVINIA - Britain's Chris Froome is on the brink of a maiden Giro d'Italia title, and a rare Grand Tour treble, after defending the leader's pink jersey in the 20th and penultimate stage on Saturday.

Spain's Mikel Nieve (Mitchelton), a former teammate of Froome's at Team Sky, capped a long breakaway with victory at the end of the 214km run from Susa to Cervinia.

Four-time Tour de France winner Froome, 33, now only has to survive the final stage in Rome on Sunday, a 115 km closed circuit race, to win his third successive Grand Tour after his wins in the Tour of Spain and Tour de France.

"We're not finished yet but the battle is behind us. It's an amazing feeling," said Froome. "This Giro has been brutal, when someone tends to have a bad day here it's not just 30 seconds or a minute, it's 10-15 minutes. You could see today (Thibaut) Pinot was in trouble and Astana turned the screw, so for us it was just to keep an eye on Tom (Dumoulin). I sprinted to the finish just to keep in front of everything."

Victory would signal a dramatic turnaround in fortunes for the Kenyan-born Briton, who before the start of Friday's 19th stage was over three minutes behind previous race leader Simon Yates (Mitchelton) and virtually out of victory contention.

The team Sky rider had suffered two falls in the first week and struggled in summit finishes. Thanks to an audacious plan concocted by his team, Froome went on the attack 80 km from the finish on the notoriously difficult Colle delle Finestre climb on Friday, leaving a struggling Yates to trail home over half an hour in arrears.

The impressive stage win gave Froome the pink jersey and left his closest rival, defending champion Tom Dumoulin, 40secs off the pace on Friday evening. With overall victory in sight, Froome gave little to the Dutchman on the 20th stage. Both crossed the finish line together as Nieve handed Mitchelton a consolation stage victory.

Frenchman Thibaut Pinot (Groupama-FDJ), meanwhile, saw his hopes of a podium finish in Rome dashed. He began the stage in third overall, but suffered a spectacular collapse. The 27-year-old Pinot started the 12 km-long climb to the Saint-Pantaleon pass among the main peloton, but crested the summit 21 minutes later and finished the stage 45 minutes in arrears. "It's a big failure, he's totally exhausted," said team sports director Martial Gayant.

Nieve, meanwhile, broke clear on the steepest part of Saint Pantaleon, 32km from the line with the Basque climber crossing over two minutes ahead of Dutch rider Robert Gesink of Team Lotto. The Spaniard celebrated his third stage win after 2011 and 2016 on the day of his 34th birthday.

"After what happened yesterday, it was very important for our team to make it up with a stage victory. Five stage wins are a lot! I couldn't have dreamt of a better birthday," said Nieve.

Froome is now on the verge of emulating cycling legends Eddy Merckx and Bernard Hinault by becoming only the third man in history to hold all three Grand Tour titles at the same time.

But this impending win could provoke more fury from his detractors. Although he has a Therapeutic Use Exemption (TUE) allowing him to use the asthma drug salbutamol, Froome tested positive for elevated levels of it at the Tour of Spain last year.

Froome escaped a provisional suspension, allowing him to compete in Italy, although the case has yet to be resolved by cycling's world ruling body the UCI.

Froome paid tribute to those who have "belived" in his innocence. "I have to say a really big part of being able to do what I was able to do was everyone believing me and everyone buying into the one plan we had," said Froome. "It just feels amazing to be able to repay them after three weeks of hard work. To finish it off today is just amazing."