Some 14,000 ready-to-eat meals and 15,000 litres (3,300 gallons) of water were dropped north-east of Port-au-Prince on Monday, the US said.
It also defended its handling of operations at the airport in Port-au-Prince. Aid agencies - and some governments - have complained at delays in access for aircraft full of equipment to help the survivors, with priority going to military flights.
"We're doing everything in our power to speed aid to Haiti as fast as humanly possible," said Gen Douglas Fraser, head of US Southern Command
Meanwhile, the UN has approved a recommendation by Secretary General Ban Ki-moon to boost UN troop numbers in Haiti by 2,000 for six months, and UN police numbers by 1,500.
Mr Ban said he was grateful to the UN Security Council for its swift action, calling it "a clear signal that the world is with Haiti".
He said the UN was in discussion with member states, and he hoped to have the extra troops and police to deploy soon. The UN mission in Haiti currently numbers about 9,000.
There have been reports of widespread violence and looting.
But the UN has played down worries over security, saying that despite violent incidents, the overall situation is calm.
US Army Maj Gen Daniel Allyn, deputy commander of the Joint Task Force on ongoing relief efforts, echoed that message, saying the security situation was "relatively calm" and that aid distribution points were orderly.
He said there were "pockets of instability", but that UN forces and the Haitian national police were addressing security needs with "agility".
AT THE SCENE
Mark Doyle, BBC News, Haiti
The Medecins Sans Frontieres hospital in Port-au-Prince was destroyed in the earthquake, so the local and international medical staff who survived set up a new treatment centre across the road in their pharmacy.
Using rough wooden sticks and a crude curtain they've established an operating theatre in the open air. The operating table is a wooden desk.
The doctors say they treated several hundred people a day in the first few days after the earthquake, and that more are coming all the time as they hear medical aid is available.
Most patients have broken or crushed limbs from falling concrete.
There were more than 2,000 US personnel on the ground and 5,000 offshore on ships, he said, adding that 10,000 troops in total would be arriving in the coming weeks, half of whom would be directly involved in distributing humanitarian aid.
Mr Ban said the UN's goal was to increase the number of people receiving food to one million this week and at least two million in the following two weeks.
Addressing concern that aid has been too slow to reach desperate Haitians, Mr Ban said the situation on the ground was "overwhelming", but that UN efforts were "gearing up quickly".
"For those who have lost everything, of course, help cannot come soon enough," Mr Ban said. "But we are working day and night."
'Test of resolve'
Last week, US Defence Secretary Robert Gates said airdrops had been ruled out because they might do more harm than good.
Mr Gates warned that they could trigger riots if there was no proper structure on the ground to distribute supplies.
The problem is dehydration but there is still a chance [of finding survivors]
But the BBC's Nick Davis in Port-au-Prince says that the US military is now securing areas on the ground before pallets of food and water are parachuted in.
British Prime Minister Gordon Brown said on Tuesday Haiti was a "test of resolve" for the international community.
France's Co-operation Minister, Alain Joyandet, had suggested on Monday that the US was "occupying" Haiti and urged the UN to "clarify" the US role.
However, a statement from President Nicolas Sarkozy on Tuesday said France was "very satisfied" with the co-operation and praised the US for its "exceptional mobilisation".
The UN says dozens of search and rescue teams are now on the ground.
On Tuesday, UN spokeswoman Elisabeth Byrs said 90 people had been pulled out alive since the earthquake, and rescue efforts were now concentrated outside the capital.
She insisted there was still hope for survivors. "The climate is mild, there are significant air pockets. The problem is dehydration but for the moment there is still a chance," she said.
Haitian officials say the death toll in the quake has risen to at least 75,000. Some 250,000 people were injured and about a million left homeless.
At least 70,000 earthquake victims have already been buried.
On Tuesday, the Paris Club of creditor governments, including the US, UK, France and Germany, called on other nations to follow its lead in cancelling debts to Haiti. Venezuela and Taiwan are the other biggest creditors.
Meanwhile, the bodies of eight Chinese nationals killed in the quake have arrived back in Beijing in a high-profile ceremony attended by relatives and top officials.
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