Hillary Clinton

"Marc and I are overwhelmed with gratitude and love as we celebrate the birth of our son, Aidan Clinton Mezvinsky," Ms Clinton tweeted.

The couple already have a daughter, Charlotte, born in 2014.

The little boy is the second grandchild for US Democratic presidential candidate Hillary Clinton and her husband Bill.

Hillary Clinton describes herself as "wife, mom, grandma" in her own twitter bio.

Gunman Omar Mateen — a New York-born Florida resident and US citizen who was the son of Afghan immigrants — was shot and killed by police early on Sunday morning after a three-hour siege, in which 49 people were killed.

His endorsement came after meeting Vermont Senator Bernie Sanders who has been battling Mrs Clinton for the nomination.

Speaking in a video tweeted out by Mrs Clinton, Mr Obama said she may be the most qualified person "ever" for the role of president.

The two are set to start campaigning together soon.

The news agency's tally puts Mrs Clinton on 2,383 - the number needed to make her the presumptive nominee.

She will become the first female nominee for a major US political party.

But rival Bernie Sanders said Mrs Clinton had not won as she was dependent on superdelegates who could not vote until July's party convention.

Mrs Clinton reached the threshold with a big win in Puerto Rico and a burst of last-minute support from superdelegates, AP said.

A speech that was billed as a major foreign policy address instead unfolded as a savage, mocking evisceration of Donald Trump Thursday as the former secretary of state adopted an aggressive new campaign persona designed to repel the unpredictable challenge posed by the presumptive Republican presidential nominee.

In one of the most striking speeches of her political career, Clinton dispensed with the sober diplo-speak that has characterized her previous national security addresses and went straight for the jugular, unleashing a series of biting attacks on Trump.

Mrs Clinton's double-digit lead, which she has held over the past several months, has vanished - and with it, apparently, Democrats' dreams of a transformational 2016 victory that would leave Republicans wandering the wilderness for a generation.

What happened? A closer look at those poll numbers offers some clarity.

Clinton leads Trump 46-to-43 percent in a NBC News/Wall Street Journal poll, compared to a similar one in April in which Clinton had an 11-point lead.

The new poll also shows Clinton primary rival Vermont Sen. Bernie Sanders leading Trump by 15 percentage points, 54-to-39 percent, in a hypothetical November matchup.

“Polls this far out mean nothing,” Clinton said on NBC’s “Meet the Press.” “They certainly mean nothing to me. And I think that if people go back and look, they really mean nothing in terms of analyzing what's going to happen in the fall.”

One Twitter user made this point — "it's only Fox so it's of no great concern" — and yes the poll was taken by Fox News, and the 45 to 42 lead is well within the margin of error so it's really a statistical tie.

However, this is a 10-point swing in Donald Trump's favour since the last Fox poll four weeks ago.

As Mitt Romney locked up the Republican nomination after 14 weeks of contests, he saw his ratings rise as Republican rallied behind their standard bearer, giving him a 4-point bounce and bringing the race against President Obama into a tie.

It took a last-minute campaign blitz and a significant financial investment for Clinton to win the Kentucky Democratic primary by half a percentage point over her stubborn primary foe Bernie Sanders — in a state she won by 35 percentage points over Barack Obama in their 2008 primary clash and where her family has deep political roots going back decades.