Donald Trump

He said the US should focus on defeating the so-called Islamic State rather than convincing Syrian President Bashar al-Assad to stand down.

Mrs Clinton has been proposing a no-fly zone over Syria, which some say could lead to conflict with Russian jets.

The Clinton campaign accused Mr Trump of "playing to Americans' fears".

Mr Trump also attacked Republicans for not uniting behind his candidacy.

"If we had party unity, we couldn't lose this election to Hillary Clinton," he told Reuters news agency at Trump National Doral golf resort in Miami, Florida.

In a video released earlier this month, the Republican nominee said he needed Tic Tacs before talking with "Access Hollywood's" Billy Bush on a hot mic about how he can do anything to women because he is a celebrity.

"I've gotta use some Tic Tacs, just in case I start kissing her. You know I'm automatically attracted to beautiful -- I just start kissing them. It's like a magnet. Just kiss. I don't even wait," Trump said.

Warren, and most every Democrat as well as many Republicans, took issue with the comments that have now rocked Trump's campaign.

The Republican nominee also said he would do "whatever you have to do to get a strong agreement," even if that meant breaking off the recently-resumed diplomatic relations.

"I just want to press -- would you break off diplomatic relations, though, on day one?" CBS4's Jim Defede asked Trump.

"I debated him for four and a half hours," she said, recalling their acrimonious exchanges. "I don't even think about responding to him anymore."

She was speaking to reporters aboard her campaign plane.

Mr Trump used a rally in Gettysburg to promise curbs on lobbying and new trade and climate change negotiations.

With just 16 days until the election, much of the recent focus has been on controversies linked to his campaign.

With 17 days until the election, much of the recent focus has been on controversies linked to his campaign.

But in a speech in Gettysburg, Pennsylvania, he sought to highlight changes he would introduce.

Among them were restrictions on lobbyists and a renegotiation on trade and climate change deals.

Mrs Clinton and running mate Tim Kaine appeared at events on Saturday in Pennsylvania, a key battleground state in the race for the White House.

Trump is set to offer up the key principles and policies driving his presidential campaign in a speech Saturday morning in Gettysburg, Pennsylvania.

The location is forever etched in American lore given that it was the battlefield where President Abraham Lincoln delivered his Gettysburg Address, though Trump will not speak at precisely the same spot.

Trump, speaking on Fox News Friday night, and his campaign aides declined to offer any substantive details of what he will address in the speech.

He also accused the first lady of attacking Hillary Clinton in 2007 by invoking a line she had said about fitness to run the White House.

The Obama campaign had denied the line referred to Mrs Clinton.

Mrs Clinton, meanwhile, accused Mr Trump of threatening democracy if he did not accept the election result.

"We know the difference between leadership and dictatorship, and the peaceful transition of power is one of the things that sets us apart," she told a crowd in Cleveland, Ohio.

Trump offered a stunning declaration during the final presidential debate that he might not accept the results of next month's election. In his first speech since the debate, Trump seemed to simultaneously double down on the stance he articulated Wednesday night while also trying to clean it up.

Trump argued forcefully during a rally here that he was being asked to "waive" his right to contest the election after critics slammed him for refusing to pledge to accept the results of the election the previous night during the final presidential debate.

In doing so, Trump missed an opportunity to take some of the heat off his campaign as it struggles through the final weeks of the race.

He opened with some more light-hearted remarks, referencing his "beautiful hands" and joking about how his crowds at rallies dwarf Clinton's.

"It's great to be here with 1,000 wonderful people. Or, as I call it, a small, intimate dinner with some friends. Or as Hillary calls it, her largest crowd of the season," Trump said, to which Clinton laughed.

But the mood turned dour when Trump began to directly take on Clinton.

Hillary Clinton was explaining her plans to raise taxes on the wealthy when she pointedly referred to Trump's possible tax avoidance: "My social security payroll contribution will go up, as will Donald's, assuming he can't figure out how to get out of it."

Trump's retort? "Such a nasty woman."

It quickly became one of the defining quotes of the night on social media.