Riise's diving header inadvertently went into his own net off Salomon Kalou's left-wing cross in the fifth minute of added time. The goal equalized Dirk Kuyt's first-half finish and makes Chelsea the favorite to advance to the final on May 21 in Moscow.
"At the end, you must be really disappointed," Liverpool manager Rafa Benitez said. "One minute in the first half, four minutes in the second half.
"Everyone was really disappointed. In these situations the only think you can do is try to be positive and try to think about the next game and be ready."
It is the third time in four seasons that the teams have met in the Champions League semifinals, but the first that Chelsea has avoided a 1-0 loss at Anfield.
"I think we deserved definitely to get the draw at the end," Chelsea midfielder Frank Lampard said. "They had chances, we had chances. It was a battle and we carried on to the end."
The previous meetings in 2005 and 2007 came as the second match of a two-leg series and sent Liverpool through. Liverpool now has to play at Stamford Bridge next week knowing it has to at least score if it is to make it through.
"These ties are decided on small details and unfortunately the little bit of luck's gone to Chelsea at the end," Liverpool captain Steven Gerrard said. "But maybe we'll get a bit of luck at Stanford Bridge.
"No fingers pointed at John; we're all in this together."
Liverpool had looked more likely to advance for most of Tuesday's match, although the first half was dominated by the kind of attrition-like, physical play that has been prominent in the majority of the previous 18 meetings between the teams over the past four years.
Fans of both sides were increasingly frustrated by passes constantly going to the opponents or even out of play.
And Austrian referee Konrad Plautz, who in this season's round of 16 angered AC Milan fans by whistling for a foul on Kaka with Philippo Inzaghi in possession and through on goal against Celtic, riled both sets of supporters for his inconsistency in calling fouls.
Kuyt and Fernando Torres had chances for Liverpool, while Joe Cole just failed to connect with a volley at the other end and Didier Drogba had an appeal for a penalty turned down when Jamie Carragher challenged him in the area.
But it was Liverpool that forced the clearest chance in the 31st, when Torres, who has scored 30 goals in his debut season for Liverpool, had a low shot saved by goalkeeper Petr Cech.
The dominance of power over finesse continued when Martin Skrtel sent a defensive clearance out of the stadium and the goal, when it came in the 43rd, was almost as scrappy.
Kuyt collected a quick free kick down the right from Xabi Alonso and, although his low cross was headed away, he won back possession on the edge of the area.
Alonso back-heeled the ball to Mascherano, whose mis-hit spun over Claude Makelele. The midfielder missed an attempted header and it dropped to Kuyt, who scored past Cech from inside the box.
Kuyt had not scored for Liverpool in the Premier League since November but has now scored in three straight rounds of the Champions League _ against Inter Milan, Arsenal and Chelsea.
Liverpool dominated the opening exchanges of the second half, with Torres and Ryan Babel tormenting the visiting defense _ the latter just shooting wide with a fierce half-volley in the 59th.
Liverpool fullback Fabio Aurelio was carried off in the 61st with what appeared to be a groin injury and was replaced by Riise, while Chelsea coach Avram Grant risked the ire of his team's fans two minutes later when he withdrew the popular Joe Cole for Kalou.
Grant's decision to replace the midfielder against Tottenham in the Premier League this season was blamed for the team's failure to hold onto a winning position, but the forward almost pulled his team level this time in the 67th with a shot that was deflected wide.
Torres almost set up Gerrard in the 83rd and, though Chelsea brought on Nicolas Anelka for Michael Ballack, giving it three strikers, Liverpool continued to look the most likely to score.
Gerrard hit a shot that was heading into the top corner until Cech got his hand to it and pushed it just over the bar.
"We had the better chances and we know we must play another 90 minutes," Benitez said. "The team today was working really hard, especially creating chances, and we must do the same away."
