The U.S. Conference of Mayors is throwing its support behind the bipartisan infrastructure deal, joining business and labor groups in urging lawmakers to pass the $1.2 trillion proposal.

The group, along with 369 mayors in all 50 states, sent a letter to congressional leaders Tuesday calling on them to “take immediate action” on the infrastructure framework backed by President Biden and a bipartisan group of senators. 

“This framework would be the largest long-term investment in our nation’s infrastructure and competitiveness in nearly a century – $1.2 trillion over eight years – to help make our economy more sustainable, resilient, and just,” the group wrote. 

In the letter, mayors urged congressional leaders to ensure that funding for COVID-19 relief efforts is not repurposed to pay for the infrastructure package. Senators have indicated that the bipartisan deal would not raise taxes, and suggested unspent relief money could be used to fund the proposal.

Senators on both sides of the aisle have expressed concern about the infrastructure plan’s funding mechanisms. 

Sen. Lindsey Graham (S.C.), the top Republican on the Senate Budget Committee, said Monday that lawmakers need to find additional sources of funding. Senate Finance Committee Chairman Ron Wyden (D-Ore.) has unveiled plans to raise taxes on corporations. 

Politico Playbook first reported the news of the U.S. Conference of Mayors’ letter Tuesday. 

The mayors’ group joins a growing list of organizations backing the bipartisan infrastructure framework. Last week, the AFL-CIO and the U.S. Chamber of Commerce endorsed the deal along with other prominent business and labor groups.

“Don’t let partisan differences get in the way of action — pass significant, meaningful infrastructure legislation now,” the groups said in a statement.