US President Barack Obama's top economic advisor Friday tried to assure China's concern about the safety of its assets in US, saying the US would be "sound stewards of the money we invest".

"This is a commitment that the president has made very clear -- we need to be sound stewards of the money we invest," said Lawrence Summers, the president's director of the National Economic Council, in a speech at the Brookings Institution, a leading think tank in the United States.

Chinese Premier Wen Jiabao said earlier Friday he is "a little bit worried" about the safety of Chinese assets in the United States, urging the US government to ensure the security of those assets.

"We lent such huge fund to the United States and of course we are concerned about the security of our assets and, to speak truthfully, I am a little bit worried," said Wen at a press conference after the close of the annual Chinese parliament session on Thursday.

China has invested its huge foreign exchange reserves in low- risk but low-yield assets, such as US government bonds, to play it safe.

According to the US Treasury, China held $681.9 billion worth of US government bonds as of November.

"China is indeed the largest creditor of the United States, which is the world's biggest economy. We are extremely interested in developments in the US economy," said Wen, adding that he is expecting the effect of the measures taken by the US government to counter the international financial crisis.

Summers, asked to react to Wen's concern during Friday's speech, noted that the United States had to utilize all resources available at present to jolt its economy from prolonged recession. "

He also said the current crisis has led to an "excess of fear" among Americans that must be broken to reverse the downturn.

"Fear begets fear," said the former treasury secretary in Clinton administration. "What we need today is more optimism and more confidence."