US quantitative easing and emerging markets' deficits are major external uncertainties for China's economy in the next half year, Vice-Finance Minister Zhu Guangyao said on Thursday.

"What if the US Federal Reserve stopped the current $85 billion bonds per month buying program? What is the impact on the US interest rate?" Zhu asked in a speech at the Global CFO Leadership Summit, which was co-hosted by Golden Finance, a finance training provider, and Shanghai University of Finance and Economics.

He said US quantitative easing is in effect lowering the interest rate to minus 2.5 percent. Even if the US exits the highly accommodative monetary policy, the de facto interest rate will still be zero.

"We should clearly recognize that even if the US exits quantitative easing and returns to the 'norm', the 'norm' would be an extremely low interest rate," he said.

The scaling back of US quantitative easing risked luring foreign capital back to the US, causing a capital exodus from China, analysts said.

The uncertainty of emerging market economies poses another risk for China's economy, he said.

"The International Monetary Fund has lowered its global growth forecast for this year to 3.3 percent. This is an important warning that global recovery and growth in the second half faces great challenges," he said.

"What is worth noting is that the IMF cited the difficulties in emerging markets, particularly the looming fiscal deficit and international balance of payments deficit in India and Brazil, and China's economic slowdown as major reasons for lowing the forecast," Zhu said.

This is the difference from last year when the IMF cited Europe and the US as major reasons for lowing growth forecast, he said.