Obama says Trump 'unfit' to serve as President, slams GOP for endorsing him

US President Obama on Tuesday slammed Republican presidential candidate Donald Trump, saying he is "unfit to serve as president" as he does not abide by norms and rules.

"I think the Republican nominee is unfit to serve as president," Obama said at a White House news conference. "I said so last week. He keeps proving it."

Obama added that Trump has shown he is "woefully unprepared to do this job" after his comments on military families as well as his handle on foreign affairs.

He slammed Trump for his rhetoric, including the one against parents of a slain Muslim-American soldier, and said the Republican presidential nominee doesn't have the judgment, temperament or understanding to be the president of the country.

As such he was highly critical of the Republican leadership who are supporting the billionaire from New York.

"There has to come a point at which you say enough," Obama said of the Republican leaders.

"The notion that he would attack a Gold Star family that made such extraordinary sacrifices on behalf of our country, the fact that he doesn’t appear to have basic knowledge around critical issues in Europe, in the Middle East, in Asia, means that he is woefully unprepared to do this job," the president said at the White House.

Obama remarked that Republican denunciations of Trump "ring hollow" as they continue to endorse Trump.

"The question that I think that 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? What does this say about your party that this is your standard bearer?" Obama said.

"This isn’t a situation where you have an episodic gaffe. This is daily and weekly where they are distancing themselves form statements he's making." 

Obama said this opinion of Trump is shared by prominent Republicans.

"I think what's been interesting is the repeated denunciations of his statements by leading Republicans, including the speaker of the House and the Senate majority leader and prominent Republicans like John McCain," he said.

"There has to be a point in which you say this is not somebody I can support for president of the United States, even if he purports to be a member of my party," Obama said.

"The fact that it has not yet happened makes some of these denunciations ring hollow. I don't doubt their sincerity. I don't doubt that they were outraged about some of the statements that Mr Trump and his supporters made about the Khan family," he said referring to the statements made by Trump against the parents of Muslim-American soldier Humayun Khan who was killed in Iraq war by a suicide bomber.

At some point, Republicans should realise that Trump has gone too far and that the things he says indicates he "doesn't have the judgment, the temperament the understanding to occupy the most powerful position in the world," Obama said.

The two-term Democratic president said this is different than just having policy disagreements.

While Obama said he has disagreed with former Republican presidents on policy issues, he did not have a doubt that they could function as president."

"I recognise that they all profoundly disagree with myself or Hillary Clinton on tax policy or on certain elements of foreign policy. But you know, there have been Republican presidents with whom I disagreed with but I didn't have adoubt that they could function as president," Obama said.

Obama explained that had he lost to Mitt Romney or McCain, he certainly "would have been disappointed," but that he would have conceded and had the confidence that they would "abide by certain norms and rules and common sense, will observe basic decency."

"But that's not the situation here, and that's not just my opinion. That is the opinion of many prominent Republicans. There has to come a point at which you say enough. And the alternative is that the entire party, the Republican Party effectively endorses and validates the positions that are being articulated by Mr Trump," Obama said.