(Advisory - please note strong language in paragraph eight)

Andy Murray of Britain serves to Denis Istomin of Uzbekistan during their men's singles match at the Brisbane International tennis tournament January 4, 2013. REUTERS/Daniel Munoz

BRISBANE (Reuters) - Andy Murray has succeeded in reaching the semi-finals of the Brisbane International but the U.S. Open champion has fallen short in a pledge to curb his habit of swearing on court.

Moreover, he has toned down the promise itself.

Last month, the Briton said he wanted to clean up his act after repeated warnings for unsavoury language, but audible obscenities have been uttered in his opening matches in Brisbane against Australia's John Millman and Uzbekistan's Denis Istomin.

Spectators at Pat Rafter Arena have clearly heard Murray barking the occasional swear word, something the world number three has done throughout his career to let off steam when dissatisfied with his own performance.

Murray defeated Istomin 6-4 7-6 on Friday to book a semi-final against Japan's Kei Nishikori, who trumped Ukraine's Alexandr Dolgopolov by an identical scoreline.

The other semi-final on Saturday will feature Bulgaria's Grigor Dimitrov against Cypriot Marcos Baghdatis.

Dimitrov beat Austria's Jurgen Melzer 6-3 6-2 after Baghdatis had taken out France's Gilles Simon 6-3 6-4.

"Obviously, me saying 'shit' or whatever is bad and wrong, and it's something I want to try to stop doing," Murray was quoted as saying last month.

However, he declined to make the same promise ahead of his clash against Nishikori.

ROLE MODEL

"I don't really know how that will go, to be honest," Murray said.

"A lot of times I get asked after matches about it. It can get picked up on the microphone or whatever. No-one has mentioned anything to me (in Brisbane) yet but the microphones at the Aussie Open are all around the court, so we'll see."

Murray denied his attempt to tone down his language was because he felt more of a role model after winning the Olympics and U.S. Open in a breakthrough 2012.

He claimed worse levels of swearing from other players went undetected because it was not delivered in English.

"Where it (the pledge to stop swearing) came from was when I got asked a question," he said.

"I was doing an interview over the phone. I got asked about swearing on the court. I said 'obviously I don't mean to do it. I don't want to do it. Sometimes you get frustrated and you do and obviously I will try to stop.'

"I didn't make any promises or guarantees that I was going to.

"Then it came out that I've said this year I will stop swearing. What I also said was that a lot of players swear on the court and a lot of people say a lot worse things than me - in other languages. It doesn't get picked up the same.

"So where I would obviously love to stop doing it, I try not to. But I can't guarantee it."

(Editing by John O'Brien)

• Please wait.

• Fernley says costs threaten some F1 teams
• Rosberg tops crash-filled final Monaco practice
• Djokovic and cold weather threaten Nadal's Paris bid
• Rosberg puts Mercedes on pole in Monaco
• Sunshine comes Just-in time as Rose blooms with 69
• Rosberg on pole for Monaco Grand Prix
• South Korea in seventh heaven
• F1 is a superego trip for Wurz's wife
• Make betting legal, says top Indian body
• NBA: Pacers edge Heat to even series