World number one and defending champion Roger Federer's Indian Wells opener was marred by rain as the wet weather forced his contest with Federico Delbonis to be rescheduled.

The score was deadlocked at 2-2 after 20-time grand slam champion Federer gracefully claimed the opening set 6-3 before rain wreaked havoc and suspended proceedings on Saturday.

Federer and Delbonis will return to centre court on Sunday, tournament organisers confirmed.

Rain – a rarity in the desert – delayed the start of the match, with Federer cautious but restless to get play underway in front of a capacity crowd.

Amid a conversation with the umpire and Delbonis on court, Federer could be heard telling his Argentine opponent: "I can start but if you don't wanna start we don't have to."

When play finally started, Federer set out to avenge his defeat to Delbonis in 2013 – the pair's only other ATP meeting.

Federer was at his trademark best, fluid and graceful as the Swiss star broke in the fourth game for a 3-1 lead and never looked back.

Delbonis, though, was not overawed, continuing to go toe-to-toe with Federer before the rain set in and fans ducked for shelter.