Reinvesting Money from Selling Stocks in USA

I am resident of UK, I get shares from my Employer, When those public stocks are vested TDS is deducted automatically. I want to sell those stocks on some profile and reinvest it again in US. Do I have to pay the Capital Gain tax? As this money is not coming back UK and reinvested in other Stocks does that also comes under Capital Gain Tax?

Hi ,
 

You have not stated which type of plan that you were in with your employer for this to be answered. Please refer to : Tax when you sell shares  . Thank you .