The New York Times had earlier reported that a number of key positions at the National Weather Service were vacant due to Trump's budget cuts since taking office, suggesting that these gaps might have hindered a prompt response to the emergency.
UN Secretary-General Antonio Guterres offered condolences through spokesman Stephane Dujarric.
"The Secretary-General is deeply saddened by the tragic loss of life," he said.
"The Secretary-General extends his heartfelt condolences to the families of the victims and expresses his solidarity with all those impacted, the people of Texas and the government of the United States," Dujarric added.
US President Donald Trump said he plans to visit Texas later this week after signing a major disaster declaration for Kerr County to ensure first responders "immediately have the resources they need."
Leavitt said Trump's visit to Texas is "tentatively" planned for Friday. She said they are trying to find the "most appropriate time on the ground," adding: "We don't want to interrupt the recovery efforts."
The flooding began late Thursday and lasted into the early hours of Friday, as heavy rains engulfed the Guadalupe River, pushing it to a crest of more than 39 feet (11.8 meters), surpassing the region's second-largest modern flood, in 1987.
