change of H1 employer

[narendra123]

Hi,

I am in India and have approved H1B petition and visa from company X, but i am planning to switch to company Y.

please give your expert comments my below questions.
1) Can I join company Y as soon as I enter US with current valid H1 visa for company X.

2) Or can I change my H1 from employer X to Y when I am in india ?

Narendra