Manager Jose Mourinho prepared for the champions' delayed kick off at a rain-swept Fratton Park by watching United open up a 12-point gap at the top with a stoppage time 1-0 win at bitter rivals Liverpool.

Top-scorer Drogba ensured that extended lead was short-lived with a superbly-taken solo goal 12 minutes before half-time to drag below-par Chelsea back into the chase before substitute Salomon Kalou grabbed a second late on.

But goalkeeper Peter Cech did just as much to deliver the victory, producing two superb second-half saves to deny Pompey an equaliser before Kalou's late goal sealed the points.

John Terry's absence caused the champions to look uncomfortable in defence in the opening moments and Richardo Carvalho gifted Portsmouth an opportunity in only the second minute, when he was caught in possession by Gary O'Neil on the edge of his own penalty area.

O'Neil's attempted centre across the face of goal was deflected behind for a goal kick by the on-rushing Lomana LuaLua.

LuaLua called Cech into action six minutes later when O'Neil had again ghosted in behind Cole and floated in an inviting cross.

Nwankwo Kanu headed the ball across the six yards box and LuaLua toe-poked it towards goal, sending the agile Cech flying down to his left to smother on the line.

It took until the seventeenth minute for Chelsea to put together their first meaningful attack when the returning Cole linked up with Andriy Shevchenko on the edge of the penalty area.

Cole bundled his way past Pompey defender Noe Pamarot and chipped a left foot shot just over the angle of David James's right hand post and crossbar.

Shevchenko was guilty of an embarrassing miss four minutes later when the 30-million-pound former AC Milan striker was played in by Arjen Robben only to slam his close-range into the side netting.

Drogba gave Chelsea a lead they scarcely deserved in the 33rd minute with another strike to add to his collection of sublime finishes.

Cole put a deep cross in behind the Pompey defence and Drogba arrived at the back post to volley a pin-point first-time shot beyond the despairing James and into the opposite corner.

Matt Taylor should have drawn Pompey level seven minutes before half time when he found himself unmarked six yards from goal after O'Neil had crossed from the right but the left back missed his kick, much to the relief of Mourinho.

The impressive Robben almost doubled Chelsea's lead within two minutes of the re-start. Dutchman Robben played a neat one-two with Drogba before bursting into the six-yard box and clipping the top of the crossbar with a left-footed shot.

Cech denied Pompey what looked like a certain equaliser when he produced a brilliant one-handed save to keep out substitute Andy Cole's point-blank header from O'Neil's Davis cross.

Czech Republic international Cech pulled off an identical stop to claw away Kanu's diving back post header less than a minute later.

Kalou put the game beyond Pompey's reach and gave the scoreline a more one-sided look when he helped himself to the visitors' second eight minutes from time.

Kalou got in between Sol Campbell and Linvoy Primus to latch onto Ashley Cole's flick and slot past James with a cool finish from eight yards.

Elsewhere, Arsenal, who must overturn a 1-0 deficit against PSV Eindhoven to stay in the Champions League next week, moved closer to ensuring a return to Europe's top table next season by beating Reading 2-1 at the Emirates Stadium.

A 51st-minute penalty from Brazilian midfielder Gilberto Silva after Gael Clichy was brought down was followed by a Julio Baptista strike as the Gunners made light of the absence of injured captain Thierry Henry.

A late own goal by Cesc Fabregas got Reading on the scoresheet but the Royals were never really in the contest.

At the bottom, Charlton provided another demonstration of their determination to beat the drop by coming back from two goals down to secure a 2-2 draw at bottom side Watford, whose own chances of survival now look virtually non-existent.

With Wigan winning 1-0 at Manchester City, the point means Charlton remained six points adrift of safety with nine games left to secure their top flight status.

Caleb Folan's winner for Wigan means they are now eight points clear of the drop zone with City the team now closest to the relegation quagmire.

Everton leapfrogged Reading into sixth place in the table after a 1-1 draw at Sheffield Utd, Mikel Arteta's penalty a quarter of an hour from the end cancelling out Rob Hulse's first-half strike for the Blades.

Fulham also had to come from behind to secure a 1-1 draw at home to Aston Villa. Norwegian striker John Carew put the visitors ahead in the 21st minute only to see his effort cancelled out within two minutes by Fulham's American defender Carlos Bocanegra.

The north-east derby between Newcastle and Middlesbrough ended in a goalless stalemate that did little to boost either club's hopes of challenging for a place in Europe next season.