LONDON, Jan 20 (Reuters) - The flow of aid into Gaza

could take time to ramp up, chief of the International Rescue

Committee David Miliband said on Monday, as relief trucks

conducted a second day of deliveries following the start of the

ceasefire.

The deal requires 600 truckloads of aid to be allowed into

Gaza every day of the initial six-week ceasefire, including 50

carrying fuel.

"That's a big step up," said Miliband, speaking to Reuters

in London. "I fear... it will take time. We want to ramp up as

quickly as possible."

He said the IRC in Gaza is focused particularly on water and

sanitation, child protection and other healthcare.

"What counts is the medicine that gets through, the water...

the fuel... the aid workers... and whether they get through

safely," he said, referring to issues with looting and security

threats to deliveries that have been a problem during the

15-month war, when aid to Gaza has been extremely limited.

In line with other humanitarian leaders, Miliband said that

funding was also needed for a sustained response in Gaza, for

what he described as "the biggest (aid) surge you can imagine,

because it's a massive emergency".

Earlier, U.N aid chief Tom Fletcher said 630 trucks had

entered Gaza on day one of the ceasefire.

Speaking ahead of President Donald Trump's inauguration in

Washington, Miliband cautioned that governments globally were

stepping back from tackling international problems despite a

rise in humanitarian need.

"I think governments are in retreat from big global

problems, and that means that NGOs and the corporate sector and

the philanthropic sector needs to step up and show what the

answers are," he said.

Trump has not outlined his plans for humanitarian aid in his

second administration, but he sought to slash U.S. funding in

his first term. The U.S. is the largest individual donor for the

IRC, Miliband said.

"We've got to make the argument it's a good investment," he

said.

"There are more resources to do more good than any time in

human history. So shame on us for not doing more good," he

added.