Attacks on Republican presidential hopeful Donald Trump abounded on the third night of the Democratic National Convention, with former New York mayor Michael Bloomberg dismissing him as a "dangerous demagogue".
Endorsing Democratic presidential candidate Hillary Clinton, Mr Bloomberg said the richest thing about Mr Trump is his "hypocrisy".
"There are times when I disagree with Hillary Clinton," he said. "But let me tell you - whatever our disagreements may be, I've come here to say we must put them aside for the good of our country.
"And we must unite around the candidate who can defeat a dangerous demagogue."
New York City has a new mayor after Bill de Blasio was sworn in at a ceremony at his home just after midnight.
De Blasio's formal inauguration ceremony will take place at on Wednesday at City Hall, where former US President Bill Clinton will administer the oath of office.
Earlier Michael Bloomberg left City Hall for the last time as mayor of New York to applause and cheers.
New York City Mayor Michael Bloomberg said he did not feel threatened or angry after two anonymous letters, believed to be carrying the deadly poison ricin, were sent to him.
The letters threatened Mayor Bloomberg and referred to the debate on gun control, according to police.
Mr Bloomberg has been one of the country's most visible gun control advocates since the shooting of 20 young children and six adults at a Connecticut school
When asked whether he was angry about the letters, he said: "No I'm not angry. There are people who I would argue do things that may be irrational, do things that are wrong. But it's a very complex world out there. And you just have to deal with them."
Two anonymous letters sent to the New York City Mayor Michael Bloomberg contained material believed to be the deadly poison ricin and referenced the debate on gun laws, police said.
Initial tests on the letters - one of which was opened in New York on Friday and the other in Washington D.C on Sunday - indicated the presence of the poison, the New York Police Department said.
Police spokesman Paul Browne said the content in both letters was "identical" and that the packages contained "an oily substance."
"One letter was addressed to the mayor personally," he added.
Emergency workers who came in contact with the letters initially showed minor symptoms of ricin exposure but have recovered now, police said.
Preliminary tests of a letter sent to the Mayor of New York Michael Bloomberg have shown the presence of ricin.
The threatening letter referenced the debate on gun legislation.
New York Mayor Michael Bloomberg has said that 1,000 NYPD officers have been assigned to counter-terrorism duties in the wake of the Boston explosions. A statement from his office said:
New York City Mayor Michael Bloomberg has taken part in his last St. Patrick's Day parade as mayor of the city:
The New York mayor Michael Bloomberg has reiterated his call for a gun law after the Connecticut school massacre:
He added: "We have heard all the rhetoric before. What we have not seen is leadership – not from the White House, not from Congress. That must end today.
"My deepest sympathies are with families of those affected, and my determination to stop this madness is stronger than ever."
New York's Mayor Bloomberg has introduced a petrol rationing scheme as three quarters of the the petrol stations in the city have been forced to close due to fuel shortages.
The system, which follows a similar rationing regime implemented in New Jersey last week, begins at 6am tomorrow morning.
New York City has been hard hit by fuel shortages since Sandy hit ten days ago.
Emergency vehicles, buses, taxis and certain other vehicles are exempt from the rationing system.
The mayor of New York Michael Bloomberg has ordered odd-even licence plate rationing of petrol in the city following Hurricane Sandy.
Under the system, petrol forecourts may only sell fuel to vehicles with license plates that end in an even number on even numbered days of the month, and vice versa.