(Reuters) - Spanish swimmer Teresa Perales is determined to eclipse Michael Phelps, the most decorated Olympian in history, by surpassing the American great's haul of 28 medals as she sets her sight on competing in the Tokyo Paralympics at the age of 44.

Perales, confined to a wheelchair since 1995 with neuropathy - a disease affecting the nervous system - won gold in the 50 meters backstroke plus three silvers at her fifth Paralympic Games in Rio this month to take her total medal tally to 26.

Unlike the 31-year-old Phelps, who retired after Rio, the Zaragoza native aims to take part in the 2020 Games in Japan.

"I didn't get all the medals I wanted but I'm still happy with the final outcome," Perales told reporters on arriving in Madrid from Rio.

"I'm two medals short of Phelps. Now I have a good excuse to continue. Now Tokyo is on the horizon.

"I hope I can make Phelps tremble but, for the time being, I'm just going to continue to train and see what happens. One step at a time."

Perales, the most decorated Paralympian of all time, took up swimming soon after losing mobility in her legs. She also suffered the loss of her father at 15 when he died of leukemia.

"You understand that nothing is more important than getting every ounce out of each day of your life," Perales said.

Her hopes of equaling Phelps' medal haul in Rio ended when the Spaniard finished fifth in the 50m butterfly final, which was followed by fourth place in the 200 freestyle final.

(Reporting by Adriana Garcia; Editing by Ken Ferris)