The International Committee of the Red Cross has said it could not keep pace with the needs of civilians caught up in Syria's worsening civil war.
ICRC President Peter Maurer said the organisation tried to exploit "cracks" in shifting combat frontlines to deliver aid to hotspots, as it had managed to do in Homs at the weekend.
However, he acknowledged that many civilians in need remained out of reach.
"We have a lot of blank spots, we know that no aid has been there and I can't tell you what the situation is," he said.
"We are in a situation where the humanitarian situation due to the conflict is getting worse.
"And despite the fact that the scope of the operation is increasing, we can't cope with the worsening of the situation," Mr Maurer told a news briefing.
The organisation has up to 30 foreign aid workers in Syria.
The ICRC has a "relationship of confidence" with the Syrian Arab Red Crescent, although the SARC's Damascus branch may be closer to the government than other branches, he said.
President Bashar al-Assad has appointed a military official to act as a conduit for the ICRC to voice its concerns on the conduct of hostilities and about respect for international humanitarian law embodied in the Geneva Conventions, he said.
A Syrian opposition watchdog estimates that 38,000 people have been killed in the 19-month-old revolt against Mr Assad.