Christine Lagarde, head of the International Monetary Foundation, has warned that the uncertainty surrounding the UK's vote to leave the EU is bad for the economy.
Speaking to Bloomberg this morning, she said businesses needed to know whether they would lose their access to passporting across the market when the UK leaves the bloc.
The uncertainty is "not healthy", she said:
One thing we know now is the timetable.
So for the next two and a half years nothing changes, but everything is changed.
She also said that a federal interest rate hike in the US would show "strong positives" for the global economy.
"If there was such a hike... presumably very gradual and well communicated... it would mean the US economy is faring better," she said. "The US is the largest player in that game."
She said that the forecasts, which included Britain falling into recession and a stock market crash, had been mitigated by action taken by central banks worldwide.
Data so far has shown a mixed picture - the IMF recently improved its gross domestic product forecasts for Britain this year.