h1 transfer or new h1 with job ?

[raradhya]

helo every one.

i have a issue with my existing H1, i am presently in UK(london) but i have H1 for a US company A, the same company had send me to work in UK. but so far i have not been to US but now i am planning to quit this company A and look for some US based company B. my question is

1. can i come to US with the existing H1 visa with out joining the company A and look for job in differnt company B and transfer my existing H1. or do i need to get a job first from Company B and come to US.

2. do i need to get a job along with the H1 from the company B for entering to US.

please reply me soon i need to decide it asap

thanks in adance
aradhya