"Don't be alarmed by the open-ended nature of it. Having no limit is a good thing because if the limit is set too low or too high, it may worry people on either sides," he said.
He also brushed aside concerns that the measure will negatively impact Thai exports by causing the baht to appreciate.
"It's not that the Thai currency will appreciate [as a result of QE3], but rather the US dollar will weaken against other currencies. So with competitors, this will hardly have any effect," he said.
He added however that in the long term, the US has to implement measures to deal with its fiscal cliff issue and reduce its budget deficit, while European Union has its own problems to solve.
Despite the minister's assurances, local financial markets are carefully monitoring foreign capital inflows after the Fed unveiled new plans to inject money into the economy, which could flood economies with excessive liquidity.
US Federal Reserve chairman Ben Bernanke announced the agency would buy US$40 billion (1.23 trillion baht) worth of mortgage-backed securities a month for an unspecific period, pending a recovery in the jobs market.
The baht appreciated by 0.8% to 30.72/79 a dollar yesterday from Thursday with the greenback weakening as investors expected increased liquidity.
But local analysts remained wary as they assess the impacts of the measure.
Teerana Bhongmakapat, dean of Chulalongkorn University's faculty of economics, said QE3 would likely have a small impact on Asian economies, which could be at risk of a slowdown due to a decline in external demand.
He said the new liquidity injected by the Fed could head to the commodities markets, particularly gold, silver and oil.
Dr Teerana said the market might overreact to the "open-ended" feature of the operation.
"For investors, the connotation of [open-ended] is excessive liquidity. But the Fed might just be referring to uncertainty in the world economy in the next year," Dr Teerana said, adding it was also unclear when QE3 would take effect.
The Fed may have left the QE3 timeframe unspecified because it wants to extend the previous liquidity injection, worth a total of $650 billion, which is about to end next month, as part of QE3.
Dr Teerana said the government and the Bank of Thailand should allow the baht to appreciate if there are foreign capital inflows rather than buying the dollar in the market or cutting interest rates to keep the baht weak.
"It is a matter of whether the government should think long or short term. The central bank has perhaps accumulated too many dollars in foreign reserves because of foreign exchange intervention in the past several years. It does not have much room to continue doing so," Dr Teerana said.
Singhachai Boonyayotin, the Bank of Thailand's senior director for the Financial Markets Department, said local assets have adjusted in anticipation of the Fed's move during the past few weeks.
The baht's appreciation yesterday was in an acceptable range and in line with the movement of currencies in the region, so the central bank did not buy dollars on the market, he said.
"The baht's appreciation could represent the market's knee-jerk reaction. We will need to monitor the trend over the next few weeks before we decide if we should act," Mr Singhachai said.
Ian Gisbourne, an analyst with Phatra Securities, said the Fed's announcement of QE3 has not changed his targets for the SET Index at 1,350 at the end of this year and next.
"There has been huge foreign investment in local stocks recently because of both economic fundamentals and anticipation of QE3," he said.