DOHA, Qatar - After winning the first seven games, No.2 seed Simona Halep overcame stern resistance from American teenager CiCi Bellis to reach the last four at the Qatar Total Open, 6-0, 6-4.

The World No.2 led by a set and a break after winning the first seven games of the match, but Bellis rebounded to keep the second set close, winning a pair of games to take her first lead.

Halep dug deep to save six break points in a key sixth game of the second set to keep herself even with the surging qualifier, and held steady late in the match to serve it out and stop a streak of three straight breaks.

"She's fast. She's hitting the ball fast, and she stays close to the baseline, which makes her game fast and it's not easy to stay there," Halep said. "You have to be aggressive to make points. In the second set, I couldn't finish the points because she was everywhere, and she has great movement."

An aggressive-minded Halep needed to be at her best to see off the teenager's dogged defense, and the World No.2 rose to the task: Halep struck 25 winners in 16 games in the match, doubling Bellis' total of 12. 

In the first set, the Romanian connected on 10 winners to just four unforced errors, and a series of extended mini-battles went her way as she worked towards a first-set bagel.

A marathon eight-deuce game on the Bellis serve, in which the American saved four break points but could not save a fifth, put Halep ahead 3-0 at the first sit-down.

That proved to be a recurring theme in the opener, as four of the six games in the set all went to deuce, but all went in favor of the World No.2.

All three breaks of the Bellis serve were lengthy affairs, but the teenager could not apply the same pressure on Halep's serve over the course of the set which took just over 30 minutes to complete.

Bellis nonetheless kept the pressure on once she got her teeth into the match, as she crunched a return winner to finally break the Halep serve and get on the board in the eighth game. 

The American saved four break points in the fifth game of the set to keep her lead, and had ample chances in the aforementioned 10-deuce affair on the Halep serve which marked the midway point of the set. 

The Romanian used the momentum to spring into the lead again, breaking Bellis' serve in response in the seventh game, but was again forced to raise her level as the 2017 WTA Newcomer of the Year showed her mettle to draw even.

Halep did just that, winning the final two games and securing her spot in the last four in one hour, 22 minutes.

"It's tough because the Top 10 are very tall, so she's like my height. I think she plays fast like everyone, but you know, now we can a little bit compare the height," Halep added of her American foe. "It's not easy for her, but she's good enough to be there.

"It was a little bit more difficult because she started to play better. I started to miss a little bit. It was good tennis, in my opinion, the second set. I'm really pleased that I could finish it, because it was a little bit stressful at the end, but the serve helped me in the last game."