The Los Angeles City Council backed a proposal Tuesday to require contractors to disclose whether they have been hired to help build a wall between the United States and Mexico, a barrier that President Donald Trump says would curb illegal immigration and tighten-up security along the border.

Councilman Gil Cedillo said the city has been clear on opposing the border wall, which is why he wants current and potential city vendors to divulge any contracts they have that would help get it built.

“This is something that we have a right to know,” Cedillo told his colleagues, prior to a vote on a motion he authored.

“We want to know if there are people who do business with the city of Los Angeles … who wish to profit from building a wall that would divide us from our nearest and dearest neighbor, Mexico,” he said.

Cedillo’s colleagues on the council agreed, voting 13-0 to request that the city attorney prepare an ordinance that would require companies retained by Los Angeles or that wish to win a contract with the city to reveal, on an affidavit, whether they have contracts “for design, construction, supply, procurement or other development-related services regarding building any proposed border wall between Mexico and the United States of America.”

Fredy Ceja, an aide for Cedillo, said the hope is to fast-track the drafting of the ordinance language and have it come back to the City Council for a vote in about two months.

Trump promised during his campaign that he would get the border wall built, and in January, he signed an executive order to do just that, with the federal government taking steps soon after to move forward with the project.

Hundreds of contractors submitted proposals to the federal government in March for border wall projects, and companies were chosen to build prototypes near San Diego.

In July, the U.S. Army Corps of Engineers began drilling and taking soil samples near the border as part of preparation for construction.

U.S. Department of Homeland Security officials also announced last week that they will use the authority granted to them by Congress to bypass environmental laws when building the border wall.

The federal budget that was passed by the U.S. House of Representatives also includes about $1.6 billion to build 74 miles of the wall.

But the effort faces some challenges. Democrats in Congress plan to fight the proposed funding for the wall, with the challenge expected to risk a government shutdown.

Environmental groups have also brought lawsuits to block construction of the wall. Meanwhile, companies that failed to obtain contracts to build border wall prototypes have lodged complaints about the bidding process, which has delayed the start of the project from this summer to October or November.