If the shutdown in Washington runs on for a month, the effects on the U.S. economy and global markets will be substantial, an IMF representative told CNBC on Wednesday.
"If it's a shutdown that lasts a month and is accompanied by financial turmoil, then the effects on the U.S. economy will be quite large and probably the rest of the world will feel them too," Jörg Decressin, deputy director of the research department at the International Monetary Fund (IMF) told CNBC Asia's Squawk Box.
Decressin's comments follow the release of the IMF's semi-annual World Economic Outlook report, and echo comments made by chief economist Olivier Blanchard at a Chicago news conference on Tuesday.
The IMF revised down its 2013 and 2014 global growth forecasts to 2.9 percent and 3.6 percent, 0.3 and 0.2 percentage points lower than its previous forecasts respectively. The IMF cited concerns over slowing growth in the emerging world for the revision.
The report came as political stalemate in Washington looked set to move into its ninth day on Wednesday, and the October 17 deadline to raise the $16.7 trillion debt ceiling loomed.
Many fear that if the Republican and Democratic parties are unable to reach a compromise on budget issues and reopen the government, the U.S. could miss the debt-ceiling deadline and default on its debt.
In its report, the IMF flagged political uncertainty as a major headwind to global growth. The body's economists have since warned that if the U.S. does default on its debt obligations, it could tip the economy back into recession.
"If there is a default then it will be very serious for the U.S. and the global economy," said Decressin.
"Almost surely the recovery in the U.S. will be derailed, there will be a recession and it could be even worse," he said.