Ranatunga, 40, who in 1996 led Sri Lanka to World Cup victory, said former team-mate Muttiah Muralitharan would win back the record after he recovers from injury.
Muralitharan, 32, known as Murali, is at home recovering from shoulder surgery in Australia.
"It is good for Murali to have stiff competition from Shane Warne," Ranatunga told AFP.
"But he will be able to get back the title very soon and then concentrate on achieving his next target."
Muralitharan has said he wants to reach at least 600 to 650 Test wickets before retiring after the next World Cup.
Ranatunga noted Murali's performance was better than Warne's because had taken 532 Test wickets in 23 fewer matches.
Warne broke the record on the second day of the second Test against India at Madras on Friday.
The 35-year-old is poised to gain a handsome lead over Muralitharan as Australia has seven more Tests scheduled this year, including five at home against New Zealand and Pakistan.
Sri Lanka play only four away Tests this year and Muralitharan's return to the squad relies on the injury healing.
"If I only hold the record for a week, at least I've got the opportunity to say I was the world record holder," Warne said in Madras.
He returned to international cricket in March after serving a 12-month ban for taking drugs.
No love is lost between Sri Lanka's Ranatunga and Warne, who he has branded a cheat. The Australian has said cricket was better off without Ranatunga.
Last month, Ranatunga slammed the International Cricket Council (ICC) for keeping Muralitharan out of the inaugural awards while recognising Warne who at the time was trailing the Sri Lankan spinner.