My Yahoo account is US market account, that means our ads are displaying only in US (I’m assuming this)

This is not a correct assumption. Your US ads appear in all sorts of places like South America & Asia among others on both Yahoo and their search partners. You can add local countries like the UK, NL, DE etc by signing up for separate accounts with Yahoo.

Have a look at [webmasterworld.com...]
and
[webmasterworld.com...]
for more information.

Thanks Tropical Island on that information.

With Reference to [webmasterworld.com...]

However wanted to know, that means account to cover UK displays ad in UK & yahoo partner site?

And Is there any way out so that I can target my ad only in US on yahoo search?

Thanks.

And Is there any way out so that I can target my ad only in US on yahoo search?

At this time no. It is rumoured that the new interface will allow geotargetting but I doubt that they will give up the revenue that their current plan provides.

However wanted to know, that means account to cover UK displays ad in UK & yahoo partner site?

If I understand you correctly a UK account should get you coverage in the UK with Yahoo & it's partner sites.

Thanks

Hope, Yahoo comes up soon with new features.