has become the second most valuable publicly listed US company, surpassing Google parent Alphabet for the first time. 

Amazon shares finished up 2.69% at $1,586.51, for a market capitalisation of $768 billion, underscoring Wall Street's confidence in its relentless expansion into cloud computing, groceries and other new businesses. 

Alphabet lost 0.39%, trimming its stock market value to $762 billion, as Wall Street fretted about regulatory fallout following revelations that a political consulting firm had improperly obtained personal data on 50 million Facebook users. 

Together, Alphabet and Facebook dominate online advertising. They have previously faced government criticism for how they employ their user data. 

Amazon's stock has surged 81% over the past year, bolstered by scorchingly fast revenue growth as more shopping moves online and businesses shift their computing operations to the cloud, where Amazon Web Services leads the market. 

Seattle-based Amazon dislodged Microsoft as the third biggest US company by market capitalisation in February. 

Apple is the world's most valuable publicly listed company, with a market capitalisation of $889 billion.

Obviously, past stock gains are not a reliable predictor of future performance, and the surge in Amazon shares in recent years has been exceptional by most standards. 

But if Amazon's stock were to keep growing on the trajectory seen over the past year, its market capitalisation would hit $1 trillion in late August. 

Apple's market cap would reach $1 trillion around a month later if its stock price continued to rise at the 25% pace seen over the past year.

Alphabet's stock has risen 4% so far in 2018 and is up 26% in the past year. 

The median of analyst price targets for the three companies put Amazon's market capitalisation at $823 billion, Alphabet's at $914 billion and Apple's at $989 billion, according to Thomson Reuters data.