Four US financial institutions, including Citigroup, have failed stress tests designed to show they could withstand a financial shock.

包括花旗集团在内的美国四家金融机构未通过可以抵抗金融动荡的压力测试。

The Federal Reserve said Citi, SunTrust, Ally Financial and MetLife failed to show they have enough capital to survive another serious downturn.

Citigroup is the third-largest US bank. The majority of the 19 tested passed.

All those tested are in a much stronger position than they were after the 2008 financial crisis, the Fed added.

The Fed tested the banks' ability to withstand a similar crisis that triggered a rise in unemployment to 13%, a 50% fall in share prices and a 21% drop in house prices.

Their strength is assessed by the amount of "buffer¹" best-quality assets, known as Tier 1 capital, they would hold if such conditions occurred.

The regulator said Citigroup had a Tier 1 capital ratio of 4.9%, with Ally Financial and SunTrust at 4.4% and 4.8% respectively.

MetLife had 6%, although it was measured slightly differently to the others.

"One problem (for Citi) is too much exposure in Europe," said Chris Lowe from FTN Financial in New York.

"It can shift its global focus, but obviously that's going to take time," he added.