Changes to the cap on state and local tax deductions as part of a major bill to fund social programs has won a commitment from President Joe Biden, according to a letter Democratic Rep. Antonio Delgado released on Thursday. 

Biden in the letter to Delgado called the provision to change the cap on the deductions — currently set at $10,000 — "a sustainable, long-term reform." 

The letter comes as the House of Representatives is working to finalize an agreement on the spending package, now known as Build Back Better. The proposal would lift the cap on deductions from $10,000 to $80,000 over the next decade.  

"I am commited to continuing our work together to deliver on this and all our shared priorities in the Build Back Better Act," Biden wrote in the letter. 

The cap on deductions, referred to commonly as SALT, was approved in 2017 as part of a tax cut package approved during President Donald Trump's administration under Republican control of Congress. The limit on the deductions affects high tax states like New York, California and New Jersey. 

Lawmakers from those states have called for the cap to be rescinded or altered before granting their support for the larger bill, including Rep. Tom Suozzi, a Long Island Democrat who has made it a signature issue. 

Biden's letter on the SALT cap to Delgado, a Democrat from the Hudson Valley now in his second term, came after a phone call between the two men discussing the issue. 

"To be in this position now and I've had direct conversations with the president who has assured me this will remain a priority that it ended up ultimately in the legislation — so to finally get it across the finish line is very important," Delgado said Thursday in an interview. 

But whether changing the cap is included in the final version of the bill depends on what happens in the U.S. Senate, where Democratic lawmakers have raised concerns about the cost of the phaseup. Delgado called the concerns misplaced. 

"This was certainly an attempt back in 2017 to harm taxpayers in New York," he said. "So everybody should be on board to make sure we restore and make sure we do all we can to work through what was clearly an attempt to harm taxpayers."

Lifting the cap beyond the current $10,000 limit will have a positive benefit for taxpayers amid rising property values in the last year, Delgado said. 

"When you put $10,000 on that cap," Delgado said, "it is a real hardship."