Biden headed to Florida to grieve with families of condo collapse

US President Joe Biden and his wife, Jill Biden, planned to travel on Thursday to Surfside, Florida, site of the deadly condominium collapse, to offer condolences to families of those killed and missing as the casualty toll climbed higher.

Biden, whose personal experience with tragedy has been a hallmark of his political career, will reprise the role of "consoler-in-chief" while rescue teams continue to search for victims in the rubble of the high-rise, which caved in one week ago as residents slept.

The confirmed death toll rose to 18 on Wednesday with the discovery of six more bodies in the ruins of the Champlain Towers South condo, including the remains of two children, ages 4 and 10, Miami-Dade County Daniella Levine Cava said. Another 145 people are missing and feared trapped in the rubble.

Nobody has been pulled alive from the mounds of pulverized concrete, splintered lumber and twisted metal since the early hours of the disaster in the oceanfront town of Surfside, adjacent to Miami Beach.

Authorities have held out hope that more survivors might be found, but prospects for further rescues have grown dimmer by the hour.

Thursday's trip marks the second time since Biden became president that he has paid a visit to the scene of a disaster.

In February, he travelled to Texas after a powerful winter storm caused serious damage to homes and businesses, left millions without power or clean water for days and killed at least two dozen.

Biden delayed his visit to Florida to avoid interrupting rescue efforts. The president has issued an emergency declaration and provided state and local officials with federal assistance to help respond to the devastating collapse.

The Federal Emergency Management Agency and US Army Corps of Engineers have deployed teams to assist with search-and-rescue, incident management and debris removal. FEMA also has coordinated with state and local officials to open a family assistance centre and provide communications support.

Biden, a Democrat, will likely appear beside Florida's Republican Governor Ron DeSantis, seen as a potential top-tier candidate to challenge Biden's reelection in three years. DeSantis has risen to power in Florida politics and built a brand as a sharp-elbowed partisan warrior, often challenging Biden on issues such as the COVID-19 pandemic and immigration.

Biden planned to use the visit to express thanks to the "heroic first responders, search-and-rescue teams, and everyone who has been working tirelessly around the clock," White House press secretary Jen Psaki said.

The president and first lady also will "meet with families who have been forced to endure this terrible tragedy," Psaki added.

Biden's gift for connecting his own hardships with the grief and anguish of others has become a defining feature of his persona, having endured the deaths of his first wife, a daughter and a son during his years in public life.

The governor and the president spoke by telephone last week, and DeSantis praised Biden for his support after the conversation.

Investigators have not concluded what caused nearly half of the 40-year-old condo complex to crumble in one of the deadliest building collapses in US history.

But a 2018 report prepared by the engineering firm Morabito Consultants ahead of a building safety recertification process found structural deficiencies in the 12-floor, 136-unit complex that are now the focus of inquiries.