Kalou extended their lead in the second half to narrow the gap to two points at the top of the table.

United face Middlesbrough tomorrow but Chelsea gave a warning they are hot on their heels.

It was just the response coach Avram Grant was looking for after the disappointing Champions League quarter-final, first leg defeat by Fenerbahce in midweek.

With Arsenal having to settle for a draw against Liverpool, Chelsea were aiming to take advantage and got off to the perfect start by taking the lead after only six minutes.

Michael Essien raced forward for the visitors and slipped a pass to Nicolas Anelka on the right.

He swept it into the area and City skipper Richard Dunne got his bearings wrong, toe-poking his attempted clearance beyond goalkeeper Joe Hart.

Chelsea kept up the pressure and Anelka scampered away in the 12th minute but as he shaped to shoot Nedum Onuoha made a crucial block.

City responded two minutes later and Michael Johnson got into a good position only to fire his effort over the bar.

Then Martin Petrov rattled a shot wide and Benjani Mwaruwari headed high over the bar while Gelson Fernandes found the arms of Carlo Cudicini with his effort in the 21st minute.

City were beginning to set the tempo and carved out a number of chances in the space of a few minutes to rattle their high-flying opponents.

Benjani and Stephen Ireland linked up in the 28th minute only for the Republic of Ireland midfielder’s effort to be blocked.

Then Petrov thumped in a fierce drive that was superbly tipped away by Cudicini at the post.

Chelsea again found themselves on the back foot and Ashley Cole hacked the ball off the line in the 31st minute, the England defender showing good awareness after Johnson’s effort had been deflected to leave Cudicini stranded.

Chelsea hit back and Kalou got clear only to send a shot wide of the post. It was a brief respite as Ireland sent a shot into the goalkeeper’s body after 38 minutes.

Petrov then found the wrong side of the post with a neat inswinging free-kick and City were growing in confidence.

Chelsea had lost some of their momentum and Grant made a change in the 51st minute, bringing on Joe Cole for Wright-Phillips.

They immediately looked more threatening and Kalou extended their lead two minutes later with a cool finish.

He latched onto a through ball from Essien and rounded Hart to find the corner for his 11th goal of the season .

Anelka almost added a third in the 55th minute only for his header to come back off the bar following a cross from Lampard.

City were forced to make a change in the 58th minute when Onuoha was stretchered off after suffering a shoulder injury in a fall.

He was replaced by Sun Jihai as they attempted to try to peg back Chelsea’s lead.

The title chasers, however, were looking dangerous every time they broke forward.

Anelka got clear down the left in the 63rd minute and picked out Kalou but his effort was blocked by Gelson Fernandes.

Petrov almost pulled a goal back with a fine free-kick that was just off target.

Chelsea, though, never looked like giving up their two-goal advantage and got the result they wanted.

City, however, are in free fall and have now won only once in seven games.