AOL announced today that it has entered into an agreement to acquire start-up and video advertising platform, Adap.tv, in a deal that is estimated to be worth $405m (£260m).

The acquisition, which is expected to close in the third quarter of this year, will enable AOL to provide publishers and advertisers with the tools to buy and sell online ads in real time. AOL made a previous offer of about $400m for the company in July, according to Business Insider.

Adap.tv was founded in 2006 and has raised a total of $48.6 million in investor funding from the likes of Gemini Israel Funds, Redpoint Ventures, Spark Capital, and Bessemer Venture Partners.

In 2012, Adap.tv supported more than 26,000 ad campaigns that ran on 9,500 websites, according to AOL.

AOL Chairman and CEO Tim Armstrong said that Adap.tv is at the "forefront" of both the programmatic trend ad and the shift from traditional TV to online video.

"AOL is a leader in online video and the combination of AOL and Adap.tv will create the leading video platform in the industry," he added. "The Adap.tv founders and team are on a mission to make advertising as easy as e-commerce and the two companies together will aggressively pursue that vision."

Adap.tv will operate independently as part of AOL's video organisation, which is led by senior vice president Ran Harnevo and part of the broader ad offerings at AOL Networks.

Adap.tv CEO, Amir Ashkenazi, said: "We believe that most TV advertising will soon be traded programmatically on platforms like ours. The combination of AOL and Adap.tv accelerates our vision of efficient and effective TV and video advertising."