Google has finalised its partnership deal with AOL, including the acquisition of a 5 per cent stake in AOL for $1 billion, Google said on Wednesday in a filing with the US Securities and Exchange Commission (SEC).

The partnership's definitive agreements, which also include a series of commercial arrangements, were signed on Friday, March 24, and the investment will close in the second quarter of this year, Google said.

For months last year, AOL toyed with the idea of ending its years-long technology and advertising partnership with Google and seeking better terms from a competitor, particularly Microsoft and its MSN Internet unit. But finally in December, AOL decided to continue using Google's search engine to power its general web search service for another five years. It also decided to keep carrying paid search ads Google sells to advertisers, from which AOL gets a commission.

The centrepiece of the expanded partnership is the stake Google agreed to take in AOL, but other parts of the agreement are also significant, such as Google's declared intention to explore, with AOL's help, the market for graphical online ads where it has until now only dabbled.

Google has previously disclosed that the agreement calls for the companies to link their respective instant message services and for AOL to assist Google with its video search service.