United Nations humanitarian chief Valerie Amos has toured the typhoon-ravaged Philippine city of Tacloban, where she says the priority is to get basic relief supplies to victims.
Amos told reporters on Wednesday that not enough supplies are getting through, five days after Typhoon Haiyan wreaked havoc in the region.
The Philippine government says the death toll from the storm has risen to 2,344. Rescue workers fear the body count could grow much higher because many remote areas have not yet been reached.
At the U.N., spokesman Martin Nesirky said blocked roads have hampered relief workers' efforts to get supplies to victims.
"It's not as if nothing is happening, it's simply not enough is happening at the speed that is required, given the number of people who require assistance," said Nesirky.
A variety of relief organizations is trying to reach out to victims.
"The World Food Program says rice has been distributed to almost 50,000 people in the Tacloban area and that 10 metric tons of High Energy Biscuits (HEBs) have been delivered so far.
The World Health Organization (WHO) says it is getting medical teams and supplies into the area, but that reaching those in need remains a challenge. So far, teams from Australia, Japan and Germany are en route or have already arrived in the region.
President Barack Obama said the United States would continue to offer whatever assistance it could as the Philippines recovers from the "awful destruction of Typhoon Haiyan."
In a Wednesday statement, Obama also said the U.S. has been offering support to Philippine Americans who are worried about loved ones in the affected regions.
In a Wednesday briefing, a senior U.S. administration official said more than 300 military personnel are on the ground in the Philippines and the number will rise above 1,000 by week's end.
Officials say the United States has provided $20 million in assistance to date, with about half going to the World Food Program.
Tweets by VOA's Steve Herman
Also, the U.S. military has used C-130 transport planes to evacuate hundreds of Philippine residents from hard hit areas.
In a VOA interview, USAID Foreign Disaster Assistance Director Jeremy Konyndyk said in spite of the initial obstacles, aid is beginning to flow into affected regions.
"We have seen a real uptick in the distribution within the last 24 hours. Some of the first really large shipments of U.S. shelter support and hygiene support were distributed over the last 12 to 24 hours. There is more of that coming," said Konyndyk.
The U.S. Navy says the carrier U.S.S. George Washington and four other ships are en route and should be in position on Thursday.
The carrier team will be able to produce millions of liters of drinking water daily.
U.S. Brigadier General Paul Kennedy, who is leading a group of U.S. Marines on the ground in Tacloban, says the "entire Pacific Command" is responding to the crisis.
He says efforts are under way to distribute water purification units and that the command is setting up equipment that will make it easier for airplanes to land in the affected regions.
Philippine President Benigno Aquino, sounding a note of optimism, on Tuesday told CNN the final toll could be significantly lower than the 10,000 figure initially given by local officials. Aquino spoke as stories of hunger, desperation and loss continued to trickle in from Tacloban.
Some information for this report was provided by AP and Reuters.