More than 80 percent of the companies that advertise on Twitter renew their marketing efforts on the microblogging service, the company's chief executive said on Wednesday.

Speaking at the D9 conference, organized by the News Corp-owned tech news blog AllThingsDigital, Twitter CEO Dick Costolo said that the Internet company's long-term success was not correlated to an initial public offering of Twitter's stock.

Twitter CEO Dick Costolo said the company counts roughly 600 advertisers, up from 150 advertisers at the end of 2010.

While Twitter has stepped up efforts to build an advertising business, Costolo said Twitter was not under pressure to boost revenue.

We don't need to optimize for short-term revenue, he said.

(Reporting by Alexei Oreskovic. Editing by Robert MacMillan)