(CN) - Republican presidential nominee Donald Trump took aim at the United State's allies among Persian Gulf states on Tuesday, saying they would not exist without U.S. help and need to do more to bring the Islamic State to heel in Syria.
The GOP standard-bearer did tacitly acknowledged that Gulf states such as Saudi Arabia, Bahrain and the United Arab Emirates are partners in the U.S.-led coalition against the Islamic State group during a speech in Ashburn, Virginia Tuesday morning, but he said if he's elected president, he will require them to finance a safe zone in Syria.
"The Gulf states have nothing but money and they're going to pay," he said," using a line he ordinarily reserves for Mexico and the wall he proposes to build to block illegal immigration along the southern U.S. border.
Trump's appearance Tuesday morning came shortly after President Barack Obama offered his strongest denunciation to date of the Republican candidate.
In a news conference, Obama reiterated comments he made last week at the Democratic National Convention, saying Trump is "unfit to serve as president."
But he then went on to urge the GOP leadership to withdraw their backing for his candidacy.
The president said the Republican criticisms of Trump "ring hollow" in the wake of his his attacks on the Muslim parents of an American soldier, Humayun Khan, who died in Iraq, 'ring hollow" if that continue to support the billionaire real estate mogul's run for the White House.
"The question they have to ask themselves is: If you are repeatedly having to say in very strong terms that what he has said is unacceptable, why are you still endorsing him?" Obama said.
Trump did not address the criticism directly, but then, President Obama's rebuke may have been the least of his problems on Tuesday. A new CBS News poll shows Democratic nominee Hillary Clinton leading him in support among registered voters 46 percent to 39 percent.
Clinton got a 4-point bump following her party's Philadelphia convention, the CBS News survey found. The latest assessment breaks the 42 percent-to-42 percent tie between the two candidates in a CBS News poll taken after the Republican National Convention.
It was not surprising then, that Trump spent much of his speech Tuesday in attack mode, hammering hard on an issue be believes is a winner his opponent's on-again, off-again support of trade deals like the Trans Pacific Partnership.
"She got pushed around by the Sanders crowd," he said, referring to the trade deal. "But she won't do what they want."
"Many [Sanders supporters] will vote for us because they like our trade policies. Our crowd is bigger than Bernie's and bigger than Hillary's that's for sure," he added.
"We're running against dishonest people. It was rigged against Bernie Sanders. He should have just gone home and gone to sleep. Instead he made a deal with the devil. He brought her half of the party," he said. "You would have thought she'd give him a bone."
