Uber shares plummeted in their hotly anticipated Wall Street debut.

They opened with a loss of some 6% in a volatile session for the broader equity market.

After pricing at $45 for the initial public offering - translating to a market value of $82 billion - Uber fell to $42 at the open on the New York Stock Exchange.

The decline was a disappointing start for a much-anticipated offering that is one of the biggest IPOs ever. 

The debut came as US-China trade tensions weighed on the stock market and follows a steady decline in value of Uber's rival Lyft since its debut in late March.

Chief executive Dara Khosrowshahi and an Uber team rang the opening bell on the New York Stock Exchange after the global ride-hailing giant raised some $8.1 billion in its initial public offering (IPO) that was among the largest ever for a tech company.

Uber's valuation in the IPO is almost a third less than its investment bankers predicted last year but still above its most recent valuation of $76 billion in the private fundraising market. 

The IPO was oversubscribed, but Uber settled for a lower price to avoid a repeat of Lyft's IPO in March, which priced strongly then plunged in trade.

Uber also wanted to accommodate big mutual funds, which unlike hedge funds put in orders for a lower price. 

Like Lyft, Uber will face questions going forward over how and when it expects to become profitable after losing $3 billion from operations in 2018. 

In meetings with potential investors the past two weeks, Uber's chief executive Dara Khosrowshahi argued that Uber's future was not as a ride-hailing company, but as a wide technology platform shaping logistics and transportation.