Natwar Gandhi told council members that Washington would have to sell around $500million in revenue bonds to build the new stadium, not the $410million Mayor Anthony Williams proposed, reports the Guardian Unlimited website.
Last month, Major League Baseball selected Washington as the new home for the Montreal Expos starting from the 2005 season.
Initially, the team will play at the RFK Stadium, while Williams has promised Major League Baseball a new stadium on the Anacostia River, fully funded by the city.
"Funds are sufficient in the 2005 budget to implement the Ballpark Act ... There will be risks, however," Gandhi said in prepared testimony.
Eric Price, deputy mayor for planning and economic development, dismissed Gandhi's assessment, saying he was being "conservative".
Gandhi's testimony was part of what is expected to be the largest public hearing ever in Washington. About 230 people signed up to speak on the controversial baseball plan, and the council said it expected the hearing to last beyond midnight.
Four of the 13 council members said they oppose the proposed financing of the project.
They criticised Williams' plan to place a large part of the burden on businesses and questioned why Major League Baseball was not covering some costs.
Williams and the D.C. Sports and Entertainment Commission argue that bringing professional baseball to the city will increase tourism and spending.
They also see the proposal as an economic development project to help revitalise the area.
