The US Fed's spending spree may undermine efforts to balance out global growth, said Ma Delun, a deputy governor of the People's Bank of China.
The Fed's program "may add risks to the global economic imbalance, put pressure on emerging markets to adjust their international balance of payments and could also stir the formation of asset bubbles," Ma said in Beijing.
Leaders of the Group of 20 economies meet on Thursday and Friday, eager to show they have not lost the cooperative spirit forged during the depths of the financial crisis in 2008.
But growing discontent over exchange rates and trade has exposed deep international rifts. If the leaders are unable to calm tensions this week, investors could grow more concerned that global cooperation is gone.
High on the worry list is protectionism. The Fed's bond-buying program has deepened concerns that the US dollar is headed lower, hurting exports from other countries.
A "trade war" could follow suit if the G20 fails to achieve a global solution for currency imbalances, Brazil's Foreign Trade Secretary Welber Barral told Reuters.
In an interview with the French media, Chinese President Hu Jintao called for the abolition of all forms or protectionism.
World Bank President Robert Zoellick called for a new global currency system, perhaps with gold as a reference point. The idea drew criticism from many policymakers and economists and there was no indication it was on the G20's agenda.
Seoul raised its security alert to its highest level due to concerns of violent anti-capitalist protests -- a common feature of past G8 and G20 summits.
Inside the security zone, keeping the political peace will be a priority for G20 leaders.
The leaders agreed last year on a "framework" for more balanced growth, which called on surplus countries such as China to bolster domestic demand while the United States and other big importers boosted savings and investment.
Despite well-publicized differences, Geithner insisted there was broad agreement among G20 members to narrow those imbalances.
"I'm very confident that you're going to see very strong consensus on this basic framework," Geithner told an audience of Indian business leaders. "The Chinese are very supportive of it. It has a lot of benefits to them."