Microsoft is considering extending its search partnership with Yahoo to territories outside the US.

Microsoft chief executive Steve Ballmer said at a news conference in Japan that the firms could extend the partnership overseas, depending on regulatory approval.

"It's possible that we would extend that partnership outside of the US," he explained. "But we'll have to wait and see until we actually are able to get approval and consummate our partnership with Yahoo inside the US, and perhaps there'll be news on that some other day."

The two companies inked a search partnership in July, in which Yahoo will use Bing to power its search results, leaving Yahoo to focus on its core business of contextual advertising. The 10-year deal is currently being scrutinised by the US Department of Justice.

Yahoo revealed last week that an agreement on the deal had been delayed, explaining that the companies still had some contractual wrangling to finish off.

"Given the complex nature of the transaction, there remain some details to be finalised," Yahoo said in a filing to the US Securities and Exchange Commission.