Juan Martin del Potro's phenomenal comeback against Marin Cilic was rewarded as Federico Delbonis beat Ivo Karlovic in straight sets to secure a first Davis Cup title for Argentina.

Sunday's opening singles rubber at Arena Zagreb proved a true classic, as Del Potro fought back from two sets down to get the better of Croatia's Cilic in a match spanning almost five hours.

That levelled the tie at 2-2 and Delbonis duly completed a convincing 6-3 6-4 6-2 victory in the decisive fifth match, thrilling the enthusiastic section of Argentinian supporters - including footballing great Diego Maradona - in the venue.

Del Potro had been on the verge of tears after completing victory over Cilic and emotions understandably ran high once again as Argentina finally broke their Davis Cup duck, following four runner-up finishes and three in the last 10 years alone.

Delbonis could have been forgiven for feeling the weight of expectation on his shoulders, yet the world number 41 held his nerve impressively to get the better of his veteran opponent.

Karlovic predictably claimed a hefty chunk of free points behind his big serve, but was punished for some sloppy play in the sixth game as Delbonis claimed the only break of the opener, before taking the set when his opponent sent a backhand return long.

The serving prowess of Karlovic got him out of a hole at 3-3 when, after he had failed to take a break-point opportunity of his own in the previous game, he fired down three aces in succession to recover from 15-40 down.

However, Delbonis continued to exploit his rival's lack of mobility and soon moved two sets up, with Karlovic appearing short of ideas.

When a hapless volley from the Croatian gave Delbonis an early break in the third set, the writing was on the wall for the hosts, whose only previous Davis Cup win came in 2005.

Karlovic saved two further break points in his next service game, but it mattered little as Delbonis cruised to victory, sparking jubilant scenes among his compatriots.