Microsoft has reached a deal with Yahoo! for an internet search partnership, ending years of back and forth negotiations.

The 10-year deal announced on Wednesday gives Microsoft access to the internet's second-largest search engine audience, adding a potentially potent weapon to the software maker's internet arsenal as it girds for an all-out assault against online search and advertising leader Google Inc.

The extended reach will allow Microsoft to introduce its recently upgraded search engine, called Bing, to more people.

In return for turning over the keys to its search engine, Yahoo! will get to keep 88 per cent of the revenue from all search ad sales on its site for the first five years of the deal, and have the right to sell ads on some Microsoft sites.