WRAPUP 2-Tennis-Open-Federer's pulsating win keeps dream alive

* Federer one victory from lifting first French Open title

* Swiss matches Lendl's record of reaching 19 major finals

* Surprise package Soderling stands in his way on Sunday

By Pritha Sarkar

PARIS, June 5 (Reuters) - Tennis fans demanded it and Roger Federer obliged -- but only just -- as the Swiss rode a wave of emotional support on Friday to move within one win of an elusive French Open crown.

Federer kept the 15,000 crowd on the edge of their seats for three hours 29 minutes before they exploded into a roar of deafening cheers when his forehand winner finally subdued Argentine warrior Juan Martin del Potro 3-6 7-6 2-6 6-1 6-4.

Just in case the message had not already been hammered home, as Federer walked off court, a male voice boomed out from the crowd: "Roger you have got to win on Sunday! Please!"

Standing in Federer's path to glory, and a record-equalling 14th grand slam title, will be 23rd seed Robin Soderling.