Global activists presented 8 million petitions to the U.N. disarmament chief on Sunday demanding a world free of nuclear weapons, kicking off a conference by world powers to review progress toward eventually achieving total disarmament.

Secretary of State John Kerry and Iran's foreign minister are both expected to speak at the conference Monday amid intense interest in the fate of negotiations over Iran's nuclear program.

The Nuclear Nonproliferation Treaty, or NPT, Review Conference happens every five years, and experts have warned that little progress is expected this time, especially with relations cool between the two largest nuclear powers, Russia and the United States.

The more than a thousand demonstrators demanded that the world's nine nuclear-armed countries do far more toward cutting stockpiles.

Many protesters were from Japan, the only country ever hit by a nuclear attack. Fragile survivors of the U.S. attacks on Hiroshima and Nagasaki 70 years ago led the way in wheelchairs.

"I hope we don't have to have the NPT five years from now!" said 83-year-old Hiroshima survivor Setsuko Thurlow.

The U.N. disarmament chief, Angela Kane, stood by the wall of boxes of petitions and told the crowd that receiving the millions of names was "very humbling." She said she had signed one of the petitions herself when she was in Japan.

Kane said she spoke Friday with U.N. Secretary-General Ban Ki-moon and told the crowd, "He's with you."

As the march made its way uptown past the Manhattan brunch crowd, some bystanders showed little grasp of the number of nuclear weapons remaining around the world today.

Guesses ranged from 120 to 150,000 to "no idea whatsoever." Experts estimate it's more like 16,000.

"Hundreds. Thousands. Doesn't matter. They're all bad," said Hal Alterwein, 75. "All you need is one nut case to blow it up."

The other nuclear-armed countries are Britain, France, China, India, Pakistan, Israel and North Korea. Only the United States, Russia, Britain, France and China have signed on to the Nuclear Nonproliferation Treaty.