The death toll of firefighters felled by 9/11-related illnesses has surpassed 300, with one of the latest victims buried Thursday following a funeral Mass in Floral Park.

Retired FDNY Battalion Chief Joseph McKie, 60, who died Sunday, was transported to Our Lady of Victory Roman Catholic Church in an America-flag-draped casket atop a fire truck. Hundreds of firefighters lined the streets to pay their respects.

At a news conference before the funeral, leaders of firefighter labor unions urged Congress to reauthorize funding for the James Zadroga 9/11 Health and Compensation Act before the money runs out in three years.

“We are unfortunately here today with the proof that … the damages are ongoing,” said Andrew Ansbro, president of the FDNY Uniformed Firefighters Association.

With McKie and two other FDNY firefighters dying in the past week from illnesses connected to their work at Ground Zero, the total is now 303, according to Ansbro and other FDNY union officials. They anticipate that toll to surpass the number of FDNY members killed on Sept. 11, 2001 — 343.

“Twenty-one years ago we lost 343 firefighters in one hour,” Ansbro said.

“It’s just become painfully obvious that we’ll be passing that number … within the next year or so,” he continued. “It’s not a milestone we look forward to, it’s just the inevitable.”

At the church on Friday, mourners lined the sidewalk waiting to get in to attend the funeral Mass for McKie. He was described as a devoted family man and firefighter — quick with a laugh and someone who fought until the end to enjoy life.

Friends said he was on a golf course as recently as two weeks before his death, albeit mostly in a golf cart.

McKie “was working on his golf swing until he could no longer stand,” his son, also named Joseph, told the mourners.

He said his father had determination and grit. Once, during a Thanksgiving Turkey Trot, a woman pushing a baby stroller passed him up, his son said. McKie started training hard, and the next year ran the New York City Marathon in under four hours, he said.

“As anyone who knew him knows, my dad cared about his family more than anything. He was dedicated to being at every holiday, birthday, sporting event, concert, and graduation he possibly could,” his son said. “He would have crawled through broken glass if it meant getting to see one more.”

McKie was also active in coaching local kids’ sports teams, according to his son.

“As a coach his teams might not have always won the big game, but he made sure we were unselfish, practiced as hard as we could, laughed a lot and loved one another,” he said. “And how then could you say we ever really lost?”

McKie leaves behind three other children, Christopher, Emily and Grace, and his wife, Eileen.

Before the funeral, Ansbro and another union official urged Congress to immediately authorize between $3 and $4 billion in new funding for the James Zadroga 9/11 Health and Compensation Act.

The legislation provides funding for first responders’ suffering health problems due to their work digging for victims for months in the rubble of the World Trade Center.

The act is named for an NYPD officer whose death was linked to exposure to toxic chemicals at Ground Zero.

Funding for the legislation will run out by 2025, Ansbro and James G. McCarthy, president of the Uniformed Fire Officers Association, reminded reporters.

Without new money, they said, services to first responders suffering 9/11-related ailments will start to be reduced.

“Never forget was something that was said 21 years ago,” Ansbro said. “We have never forgotten, and we plan to make sure that the politicians down in Washington don’t forget and they continue to fund this program.”

He and McCarthy said it is the third round of trips they must make to Washington, D.C. to convince legislators to fund the program.

“It is frustrating going down there every few years to renew our calls for funding,” Ansbro said.

Another NYFD member, retired Capt. Michael Dugan of East Northport, was even more forceful.

“It’s shameful that we have to go to the government and ask for funding for what we need after what we did for this country,” Dugan said.

“We are going to pass that number of 343 and keep going until every one of us who was there on 9/11 is dead,” he added. “We live with it every day.”

Union officials said more than 1,000 FDNY members who worked on “The Pile” at the World Trade Center have been diagnosed with cancer, and some are already in hospice.

The number of those dying is “accelerating, there’s no question about it,” Ansbro said.”