GENEVA - Western states should enact policies to prevent asylum seekers embarking on dangerous routes, the U.N. refugee chief said on Thursday, as the number of migrants through the Darien Gap this year tops half a million people.

Conflicts, poverty and climate change have driven a record 114 million people from their homes around the world while Western governments are under growing domestic pressure to get tougher on asylum seekers, with some considering schemes to deport them.

The Darien Gap, a notorious stretch of jungle in Panama, has become a treacherous part of the journey for tens of thousands of people trekking across the Americas, hoping ultimately to reach the United States.

"There's a lot that can be done, but it's not being done and then we end up always having people at borders of rich countries and this becomes a big affair of state," Filippo Grandi, United Nations High Commissioner for Refugees (UNHCR), told Reuters.

Citing Panama's data, UNHCR said on Thursday that 500,330 people had crossed the Darien Gap so far this year which is double last year's previous record.

Many are subject to robbery, sexual violence, human trafficking, extortion and kidnapping along the way, it said, warning of a "deepening humanitarian emergency".

Grandi praised as a "good first step" a series of 'safe mobility' deals agreed between the United States and regional governments to address humanitarian issues and allow refugees and migrants to apply for entry far from the U.S. border.

However, he said Washington also needed to do more to make its system more efficient, citing a backlog of hundreds of thousands of cases. And he said the opening of these new offices did not justify turning away asylum seekers at the border.

"It should not be at the expense of people that are still arriving," he said. "I think it's a model that also Europeans could look into to establish, but it requires a lot of cooperation," he said.

(Reporting by Emma Farge; Additional reporting by Ted Hesson; Editing by Alexandra Hudson)