As a Nato summit opened here amid protests, the US failed to strike a deal with Pakistan to reopen supply lines to Afghanistan casting a long shadow over talks to end the alliance's combat role in the Afghan war.
US President Barack "Obama remained at loggerheads with President Asif Ali Zardari of Pakistan, refusing even to meet with him without an agreement on the supply routes," the New York Times reported. It also cited officials in both countries as saying a deal would not be coming soon.
Zardari, who flew to Chicago with hopes of lifting his stature with a meeting with Obama, was preparing to leave empty-handed, it said, amid continued tensions over US air strikes in November that killed 24 Pakistani soldiers leading to the closure of the supply routes.
Zardari did, however, meet with secretary of state Hillary Clinton to discuss the supply routes, said a report citing Ben Rhodes, a deputy US national security advisor. However Rhodes gave no details.
Meanwhile, protesters clad in black clashed with police at the end of what had been a peaceful march and rally by thousands of demonstrators, led by disenchanted veterans of the Iraq and Afghan wars protesting the opening of the two-day Nato summit.
The demonstration was the largest Chicago has seen in years, according to ABC News.
The battle between protesters believed to be members of the anarchist group Black Bloc and police left several demonstrators bloodied, and marred what had been a solemn and orderly march.
At the end of the march, the vets threw their Nato medals over the fence set up by the secret service around McCormick Place.
Earlier, three men were arrested on terrorism charges Saturday. They are accused of building Molotov cocktails and planning attacks at Obama's Chicago campaign headquarters and at the home of Chicago Mayor Rahm Emanuel during the Nato Summit, prosecutors said.
Brian Church, 20, Vincent Betterly and Jared Chase, both 24, were charged with conspiracy to commit terrorism, providing support for terrorism and possession of an explosive or incendiary device.