New York, New York - New York has sued bus companies transporting migrants from the southern border to the city for $708 million, the mayor said on Thursday.

For more than two years, Texas Governor Greg Abbott has chartered coaches to move newly arrived migrants from the border to New York and other Democratic-run cities in protest at what he claims is the national government's failings on immigration.

New York had sought to curb the arrival of buses carrying migrants by newly limiting where they could drop passengers and introducing prior notification requirements.

But those requirements, introduced amid an increasingly bitter row that has become a core campaign issue ahead of this year's presidential election, have been circumvented.

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Some buses carrying migrants have dropped off passengers in neighboring New Jersey, from where they make the last leg of their journey to New York by railway.

"[The city] announced a lawsuit against 17 charter bus and transportation companies that seeks to recoup all costs New York City has incurred providing emergency shelter and services to migrants transported by the charter bus companies – totaling at least approximately $708 million in the last 20 months," the city said in a statement.

"Since the spring of 2022, Texas Governor Greg Abbott has admitted to facilitating the transport of more than 33,600 migrants to New York City without having the companies transporting those migrants pay for the cost of continued care in violation of New York's Social Services Law."

That law requires city authorities to provide shelter and care to anyone in the Big Apple who requests it.

"These companies have violated state law by not paying the cost of caring for these migrants, and that's why we are suing to recoup approximately $700 million already spent to care for migrants sent here in the last two years by Texas," said New York Mayor Eric Adams.

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On Wednesday, the Justice Department sued Texas to overturn a local law that creates two new state crimes in an effort to control migration.

"States cannot adopt immigration laws that interfere with the framework enacted by Congress," said Associate Attorney General Vanita Gupta in a statement.

New York, a megacity of 8.5 million inhabitants, has welcomed waves of migrants throughout its history, and more than 164,500 asylum seekers have arrived since spring 2022, city hall says. Over 68,000 of them are still being cared for by the city, which has opened 214 sites to shelter them, mostly repurposed hotels.

The influx of migrants has become a central issue as campaigning ramps up ahead of November's presidential polls, and the United States is seeing record numbers of arrivals on its southern border.

The number of people seeking to enter the United States without authorization had shot up last month to around 10,000 a day, nearly double the number from before the coronavirus pandemic.