Cilic, rested for the first singles, had won Saturday's doubles with Marin Draganja.
"It was extremely good tennis and I'm extremely happy to be back in the World Group with my team," Cilic said on court. "We have a young team and we're only going to be able to improve."
Almost unthinkably for a nation blessed with so many top 100 players, Spain will not be in next year's World Group after they were relegated following defeat against Brazil on an indoor claycourt in Sao Paulo.
Roberto Bautista Agut's 6-4 3-6 6-3 6-2 defeat by Thomaz Bellucci in the first reverse singles after the visitors trailed 2-1 overnight means Spain will be missing from the elite for the first time since 1996.
They have won the title five times since 2000 but this year they have been weakened by the absence of a host of big names including Rafa Nadal and David Ferrer.
Croatia, the 2005 champions, and Brazil will be joined in the World Group by Belgium, Australia and the U.S who all triumphed at the weekend in their playoff ties against Ukraine, Uzbekistan and Slovakia respectively.
Argentina, finalists three times since 2006, came from 2-1 down on Sunday to beat Israel 3-2 and maintain their World Group status in a tie moved to Miami from Tel Aviv some weeks ago due to the fighting in the Middle East.
India and Serbia were locked at 2-2 in Bangalore where heavy rain meant the deciding singles rubber between Yuki Bhambri and Filip Krajinovic was not possible.
Canada also progressed to the World Group as Milos Raonic beat Santiago Giraldo in straight sets to give his side an unassailable lead against Colombia in Halifax.
This year's final will be between France and Roger Federer's Switzerland. France saw off defending champions Czech Republic while Federer gave the Swiss victory against Italy.
(Writing by Martyn Herman, editing by Mark Meadows)
Share
