Some of the nation’s leading businesses are prodding lawmakers to act on immigration legislation as the issue enters a critical phase on Capitol Hill.

In a letter to be released today, the chief executives of Coca-Cola, McDonald’s, Loews Hotels, Tyson Foods, Cargill and a half-dozen other national and regional companies say that without action to overhaul ineffective immigration laws and allow lower-skilled workers into the country legally, their businesses cannot ensure the workforce they need.

“This is indispensable for our businesses, but it’s also critical for the nation,” the executives write. “Without a workable temporary visa program, the U.S. can have no hope of ending illegal immigration.”

The letter comes as House Republican leaders confront a narrowing window to act on overhauling immigration laws nearly a year after the Senate passed a bipartisan bill with a path to citizenship for the millions now here illegally.

The Senate bill also included billions of dollars for border security and a new visa program for lower-skilled workers, like the one sought by the authors of the business letter. They note that there is presently no real way for lower-skilled workers without family in the U.S. to come here legally for year-round employment.

“Congress has an obligation to fill this gap,” they write.

Many business lobbyists, advocates and others believe that if Congress does not act before leaving Washington for an annual August recess, there will be no chance of passing immigration legislation this midterm election year, and likely not until a new president has taken office in 2017. They are focused intently on the next month or so as the best and final opportunity to get the issue moving in the House.

Although House Speaker John Boehner has not publicly indicated any plans to bring bills to the floor, a small group of lawmakers and aides is working behind the scenes to ready legislation in case the opportunity emerges.

Meanwhile outside advocates and White House officials are working hard to keep immigration in the spotlight. President Barack Obama met at the White House Monday with a group of nurses to discuss the issue, which is one of his top second-term priorities.

If Congress doesn’t move by August, Obama is widely expected to act on his own executive authority to take steps to curb deportations, which have reached record highs on his watch.