With an anxious world watching, Americans began voting Tuesday on whether to send the first female president or a volatile populist tycoon to the White House.

The kickoff marks the end to a campaign like no other -- exhausting, often bitter -- as Hillary Clinton and Donald Trump presented radically different visions of how to lead the world's greatest power.

Police quickly apprehended a 46-year-old white male in the shooting death of two police officers who were "ambushed" in separate attacks in the U.S. state of Iowa early Wednesday, authorities said.

Scott Michael Greene from Urbandale -- a suburb of state capital Des Moines -- was captured less than two hours after police released his name and said they were searching for him. They had cautioned that Greene should be considered armed and dangerous. 

For hardliners in Iran, running down the United States has become a lot easier during the U.S. election campaign -- it's just a matter of turning on the television.

Convincing North Korea to abandon nuclear weapons is a "lost cause," America's top intelligence official said Tuesday, causing concern in the State Department and ally South Korea over an issue of long-standing U.S. policy.

The United States has always maintained it cannot accept North Korea as a nuclear state and, under President Barack Obama, has made any talks with the North conditional on Pyongyang first making some tangible commitment towards denuclearisation.

The United States on Tuesday denied charges from WikiLeaks that Washington asked Ecuador to cut the internet connection of the website's founder Julian Assange.

WikiLeaks on Monday alleged that Assange's internet access was cut Saturday after the anti-secrecy published private speeches by Democratic presidential nominee Hillary Clinton to Goldman Sachs.

Iran has rejected remarks by U.S. Secretary of State John Kerry that its policies in Syria and Yemen are blocking efforts to encourage banks to do business with it.

Bill Clinton created fresh problems for his presidential candidate wife when he criticized the way U.S. health care works under Barack Obama's reforms as "crazy," prompting Republican Donald Trump to seize on the misstep Tuesday.

The former president has a reputation for speaking in a more freewheeling style than Democrat Hillary Clinton does on the campaign trail, and his remarks in Flint, Michigan created a hiccup for his wife at a critical phase in the White House race just five weeks from Election Day on November 8.

Tens of thousands of Americans have already cast their votes for Hillary Clinton, Donald Trump or other candidates well ahead of November's presidential election, part of an early voting tradition that is gaining popularity.

With 35 days still to go, it has not yet been a voting deluge. According to professor Michael McDonald, an early voting specialist at the University of Florida, about 130,000 people have already voted -- out of 130 million expected voters.

U.S. Secretary of State John Kerry insisted Tuesday that Washington was still seeking peace in Syria, but said it had dropped ceasefire talks with Russia because of "outrage' over Moscow's support for the regime.

Hillary Clinton and Donald Trump battled to break out of deadlocked polls Tuesday after clashing in their first televised debate, lashing each other with insults on the campaign trail in critical states.

An exuberant Clinton came out swinging, condemning her Republican rival as "dangerously incoherent" with an energy that suggested she was exiting perhaps the worst period of her 15-month campaign beset by blunders in belittling Trump supporters and laid up with pneumonia.