The scale of destruction in Syria is on a level not seen since the Second World War, a charity head has said.
Red Cross chief executive Mike Adamson likened the damage caused during the ongoing civil war to the aerial bombardment of London and Dresden more than 70 years ago.
More than half of Syria's 22.8 million pre-war population have been displaced within the country and across its borders in search of safety.
The Syrian conflict will enter its seventh year this week.
Mr Adamson has just returned from a four-day trip to Syria - his first to the war-ravaged country - where he witnessed the shattered ruins in Homs.
"When you see the destruction of the old city and then the flats and houses that people used to live in - there is no prospect of people being able to return quickly even if the situation is stable, because the scale of destruction... I've never seen anything like it," he said.
"It's on World War Two scale, in terms of those images we have from the Blitz or Dresden bombings."
More than half of the city's 2,000-strong population has fled to other parts of Syria or across the border to neighbouring countries since the start of the conflict, the charity said.
As the sixth anniversary of the protests which sparked the conflict approaches, Mr Adamson said it was hard now to see a "pathway to resolution".
He said: "The scale of it is quite hard to get your head around. There's loss of life, and then there is just a colossal loss of opportunity for a nation.
"I've been in a range of disaster situations over the years with the Red Cross, I've never quite had this sense of the scale of loss of life, opportunity, livelihood, and of a nation set back by decades.
"Even if peace arrived tomorrow it would take decades to rebuild because so much has been destroyed."
Mr Adamson also praised the "humbling" generosity of Syrians who would offer him tea as he visited their damaged homes.
Aid workers were risking their lives daily, he said, adding that he heard of one volunteer who had been kidnapped 10 times.