Atlanta Mayor Kasim Reed continued his push in support of a region-wide transportation tax vote on Sunday, telling a national transit group gathered at a downtown hotel that Atlanta risks being left behind unless it unclogs its congestion.

Reed said the $600 million that would flow to MARTA for capital projects under the $6.14 billion regional project list would help sustain Atlanta's huge tourism industry.

"Folks need to be really careful with the MARTA jokes," Reed told reporters. "We compete all over the globe for major tourism and conventions. It impacts tens of thousands of jobs."

The T-SPLOST, as the tax is commonly called, has attracted opposition from an unlikely coalition of conservative Tea Party members and transit advocates who say the project list is too heavily weighted towards roads. Last Sunday, state Sen. Vincent Fort visited four local churches to argue against the tax.

"These folks have $8 million wanting you to vote for the T-SPLOST, but what they are not telling you (is) when you go to the store to get your milk and bread, you are going to have to pay an extra penny," Fort told the congregation at new Calvary Missionary Baptist Church last week.

In three separate surveys conducted for the Untie Atlanta campaign in recent weeks, support for the tax fell from 51 percent to 38 percent.

On Sunday, Reed fired back at critics, saying they "haven't put up a single alternative."