STRASBOURG: The European Parliament on Thursday condemned the United States' treatment of migrants arriving at its border with Mexico, drawing a rebuke from the American ambassador in Brussels.

The parliament passed a motion deploring what it called the "appalling conditions" in US immigration detention facilities as President Donald Trump takes a tough line on the flow of undocumented migrants coming to the country from Central America.

Gordon Sondland, the US ambassador to the EU, said the parliament had "missed the mark", and that Washington was seeking to protect legitimate asylum seekers while deterring "those with false/meritless claims".

The non-binding motion -- passed by 330 to 252, with 55 abstentions -- condemned the separation of migrant families, saying it appeared to be "a tool of immigration policy aimed at deterring people seeking safety".

And it voiced concern at "the appalling conditions in which migrants and asylum seekers, particularly children, are held in US immigration detention facilities, which lack adequate healthcare, decent food and proper sanitation".

The number of migrants detained by the US Border Patrol surged to a 13-year high of more than 144,000 in May before easing to 104,000 in June -- still up 142 percent from a year earlier.

Most are families from Guatemala, Honduras and El Salvador.

The large number of migrants has overwhelmed the capacity of US officials to house and care for them, with many, including children, being held in squalid conditions for weeks as they await processing.

Sondland wrote on Twitter than the US "welcomes diversity & migration but it needs to be secure".

"We're working with partners to improve the lives and security of citizens in Guatemala, Nicaragua and El Salvador to combat human trafficking, assist LEGIT asylum seekers and those fleeing persecution. Must deter those with false/meritless claims," the ambassador wrote, adding that Washington was increasing resources to deal with the crisis. —AFP