The Royals belied their lowly Championship standing to produce one of the biggest FA Cup shocks of the third round after the Reds had looked on course to progress courtesy of Ryan Bertrand's 45^th minute own goal.

But Gylfi Sigurdsson's 90^th minute spot-kick forced the game into extra-time, leaving substitute Shane Long to grab the headlines when he stooped to head home the winner 10 minutes later.

A night of high drama had begun with the news that the Reds had secured the free transfer signing of Maxi Rodriguez and the Anfield faithful were treated to a brief glimpse of our new Argentine star prior to kick-off.

It was enough to help warm the palms of the supporters who had braved the icy conditions; the majority of whom were eager to see the Reds mark their first home match of 2010 with a win.

The boss had opted to make five changes to the side that drew 1-1 at the Madejski Stadium, and while Liverpool started brightly, it was the visitors who looked the more likely as the half wore on.

The home side went close on three minutes when Steven Gerrard's devilish right-wing centre was almost turned into his own net by Bryn Gunnarson while at the other end Gylfi Sigurdsson forced a smart save out of Diego Cavalieri, who was making his fourth appearance of the season in place of Pepe Reina.

Dirk Kuyt then saw a goalbound effort well blocked before Fernando Torres dragged wide from the right side of the area.

The Royals' game-plan was to hit Liverpool on the counter attack and it almost worked to perfection on 21 minutes when they should have snatched a shock lead.

Simon Church, who scored the goal that earned the Championship outfit a 1-1 draw in the first meeting, broke down the right before cutting past Daniel Agger with ease. The Welsh forward sent a dangerous cross to the far post, where Grzegorz Rasiak arrived and stabbed over with the goal gaping.

The threat on the break was there for all to see and the away side came within a whisker of opening the scoring again just two minutes later, when Church somehow failed to connect with Jobi McAnuff's sublime cross.

It wasn't quite going to script for the Anfield faithful and Benitez's men suffered another blow on the half hour mark when Torres limped out of the action. It was a frustrating sight for the Reds boss, who will now face an anxious wait to see if the Spain international will be forced to miss the forthcoming matches against Stoke and Spurs.

With half-time approaching Liverpool had barely mustered a shot on goal, although Yossi Benayoun did go close when his instinctive curler arced inches past the post after a forceful run from the right by Philipp Degen.

In truth, the Royals were good value to go in level at the interval, but all their hard work was undone on 45 minutes when Bertrand deflected Gerrard's cross into his own net.

The half-time tea must have tasted that much sweeter for Kopites but they would have been well aware that the Reds needed to crank it up a gear if they were to remove any lingering thoughts of an upset - and they would have to do that without Gerrard, who was replaced by Ryan Babel.

The hosts were now without their two most attack-minded players, but as the second period got underway, there was a significant improvement in Liverpool's approach.

Kuyt went close to doubling the advantage with two snap shots before Agger fizzed a 25 yarder just wide after Alberto Aquilani struck the wall with a free-kick.

Reading were struggling to make any inroads on Cavalieri's goal but almost grabbed an equaliser on 67 minutes when Ivar Ingimarsson somehow failed to connect with a right-wing free-kick.

With chances at a premium, the visitors knew they would have to take any that came there way and there were none better than when McAnuff broke clear 10 minutes from the end.

The winger enjoyed an impressive display at the Madejski and almost capped his appearance at Anfield with a goal when he slalomed past three Reds challenges, only to slot his effort wide of the post with Cavalieri beaten.

It set up a nervy finale for the home side and just when it looked like they would edge to victory, the visitors were handed a stoppage time lifeline.

Benayoun was adjudged to have brought down Long in the penalty area, leaving Sigurdsson to step up and coolly send Cavalieri the wrong way from the spot.

The first period of extra-time saw Liverpool gain the ascendancy and after Agger's free-kick deflected wide, Babel forced Adam Federici into action with a low shot.

At this point the Reds were looking the more likely but on 100 minutes they were left stunned as Long stooped to guide a header past Cavalieri following a powerful run and cross from Gunnarsson.

Benayoun then had a chance to restore parity but hit a tame strike straight at Federici after bursting clear on goal.

With time running out, the frustration became tangible inside Anfield and although Ngog and Kuyt went close to levelling, Reading held firm to secure a famous triumph.