Boonen won a sprint finish to end the 147km ride from Al Thakira to Madinat Al Shamal, to see off Dutchman Tom Veelers and Swiss Fabian Cancellara.

It was Boonen's second win of the 2012, he also won the opening stage.

“This is an important step towards the general classification,”Boonen said.

“The more difficult the race conditions, the more the riders who are in top shape are emerging. Today our team had a perfect race. Once again Steegmans carried me perfectly. I have great faith in Gert and again today we proved our worth.”

Boonen leads the general classification by 31 seconds over Tyler Farrar in second and Juan Antonio Flecha in third, 34 seconds adrift.

“It won’t be easy to defend the jersey in these next few days but I’m lucky to have a great team with me,” Boonen said

“Personally, I feel good and I’m looking forward to the last stages with confidence, even if in the desert flat tyres and echelons are part of the course.”

Thursday's fifth and penultimate stage is a 160km ride from Camel Race Track to Al Khor.

Stage 4

1. Tom Boonen (BEL), 3hr 03min 14sec
2. Tom Veelers (NED) same time
3. Fabian Cancellara (SUI) s.t.
4. Juan Antonio Flecha (ESP) s.t.
5. Gert Steegmans (BEL) at 4sec
6. Nikolas Maes (BEL) 11
7. Yoann Offredo (FRA) 14
8. Bernhard Eisel (AUT) s.t.
9. Tyler Farrar (USA) s.t.
10. Ian Stannard (GBR) 36

Overall classification

1. Tom Boonen (BEL) 9hr 50min 50sec
2. Tyler Farrar (USA) at 31sec
3. Juan Antonio Flecha (ESP) 34
4. Gert Steegmans (BEL) 36
5. Bernhard Eisel (AUT) 45
6. Tom Veelers (NED) 1:00
7. Fabian Cancellara (SUI) 1:06
8. Ramunas Navardauska (LTU) 1:09
9. Aidis Kruopis (LTU) 1:10
10. Adam Blythe (GBR) 1:14