New York/ Hong Kong (CNN Business) Oil prices have already given up gains posted early Monday after OPEC+ reached an unprecedented deal to slash production, while global stocks slumped ahead of a week chock full of reports that will offer a look at how major economies and corporations have been hit by the coronavirus.

US oil futures were little changed below $23 a barrel after gains of 5% evaporated as traders took a closer look at a deal to slash oil production by 9.7 million barrels a day, starting next month. Futures for Brent, the global benchmark, gave up similar gains to trade 0.3% lower at $31.38 a barrel.

The deal is meant to help stabilize the energy market , which has been rocked by a price war and the coronavirus pandemic. But analysts say it doesn't go far enough, given the collapse in global demand for transport fuels triggered by lockdown measures to contain the virus.

Nikkei 225 N225 Kospi KOSPI Shanghai Composite SHCOMP In stocks, Japan'sand South Korea'sfell 2.3% and 1.9%, respectively. China'slost 0.5%. Markets in Hong Kong and Europe remain closed for the Easter holiday and will reopen on Tuesday.

Dow INDU S&P 500 SPX Nasdaq COMP Meanwhile,futures fell 140 points, or 0.6%.futures andfutures were also down about 0.5% each.

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