L1 B Rejected twice any possibility of getting rejected for Tier 1 (General)

[frnd]

I like to apply for Tier 1 (General) Visa for UK. L1B Got rejected Twice for me for US . But there is no rejection stamping in my passport.

In vaf9 form(Tier 1 General Application Form), in section 6.3
6.3 Have you ever been refused a visa for any country including the UK?

Whether i have to mention these US rejection details in the application?
If i mention all these details any possibility of UK Tier 1 (general) visa getting Rejected?

Please help me in this . its very urgent ...