U.N. officials also said more than 900,000 people had been displaced by the storm and nearly 12 million people had been affected by it in some way, NBC News reported.
The U.N. death toll of 4,460 was nearly double the 2,357 tally the Philippine government announced earlier Thursday.
Earlier this week, President Benigno Aquino III predicted the toll would be 2,000 to 2,500, saying "emotional drama" influenced some to give higher estimates.
The non-government agency also warned that the devastated city of Tacloban could run out of fuel within days.
Also Thursday, the USS George Washington arrived off the coast of the Philippines.The aircraft carrier's 5,000 sailors and two supporting cruisers began moving aid to the increasingly desperate survivors of Typhoon Haiyan, known in the Philippines as Yolanda, considered one of the most powerful storms ever. The storm, with winds of up to 195 mph, made six landfalls Friday as it laid to waste a large swath of the island nation.
In Washington, President Obama said Haiyan and its aftermath were a "heartbreaking reminder of how fragile life is."
Obama said the George Washington and other ships would help in search-and-rescue operations and provide logistical support as well.
"And more help is on the way," he said without elaborating.
"As I told President Aquino earlier this week, the United States will continue to offer whatever military assistance we can," Obama said.
Valerie Amos, the U.N. humanitarian chief, told reporters the slow pace of aid distribution left her and others feeling like "we have let people down."
"I do feel that we have let people down because we have not been able to get in more quickly," Amos told reporters in Manila Thursday. "I think we are all extremely distressed that ... we have not managed to reach everyone."
She said the immediate priority for humanitarian agencies in the near term was to transport and distribute high-energy biscuits and other food, tarpaulins, tents, clean drinking water and basic sanitation.
Meanwhile, Aquino faces the challenge of containing rising anger and deteriorating security, which also concern humanitarian workers, NBC said.
"The Tacloban team is facing enormous constraints because we cannot move around freely due to the security situation," said Elisabeth Byrs of the World Food Program.