Al Gore is refusing to endorse Hillary Clinton for president until she wins the Democratic nomination.

The former vice president has stated many times in the past that it was too early to endorse Clinton or her rival Bernie Sanders, but revealed on Today Monday morning that he will not back either candidate until they win the primary.

When asked if he had been approached by Clinton or Sanders for an endorsement, Gore said; 'I've gotten signals that you could interpret that way.'

Despite this, and the fact that Bill Clinton endorsed Gore before the start of the 2000 primary when he made a run for the presidency, Gore is not throwing his support behind Clinton or Sanders until they have sewn up a primary victory.

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Not doing it: Al Gore revealed on Today Monday morning (above) that he is refusing to endorse Hillary Clinton over Bernie Sanders

Back in the day: President Clinton (above with Hillary and Gore in January 1997) endorsed Gore when he ran for president in 2000 over a month before the start of the primary

Gore did manage though to praise both Clinton and Sanders for their stance of climate change during the interview, while voicing his concern about what could happen in Donald Trump was elected president.

'He has said some things on the climate crisis that I think should concern everyone,' said Gore, pointing out Trump's past comments that global warming is a hoax.

Gore then added that he did have some hope, saying; 'President Carter said that he hopes [Trump] will be malleable, so I don't know.'

He also revealed he has allies in the Tea Party who support his beliefs on global warming, referring to them as the 'Green Tea Party.'

Gore first revealed he would not back Clinton in the primary last November, with a member of his team saying in an email to Politico; 'He has great respect for and long-standing relationships with all of the candidates running for the Democratic nomination for president.

'He appreciates the emphasis each of the candidates has placed on advocating for solutions to the climate crisis and will do all that he can to ensure that climate change remains a priority throughout this debate.

'However, he has no plans to endorse a candidate in the Democratic primary.'

Gore did the same thing in the 2008 primary, refusing to endorse Clinton and later throwing his support behind President Obama after he won the party's nomination.

Politico spoke to Democratic insiders who suggested that Gore may not be endorsing Clinton because of their history and events that happened while she was first lady.

One insider said Gore became upset when President Clinton asked his wife to work on convincing Congress to pass comprehensive health care reform rather then giving the task to his vice president.

'Usually you give your vice president something of that level. You don’t give it to the first lady,'explained the insider.

'People forget that sort of started the relationship on a downward spiral early on.'

Popular guy: said that he had 'gotten signals' that both Clinton and Sanders (above on Sunday) were seeking out his endorsement

Others claim that Gore is still upset because Clinton's New York Senate run in 2000 took the focus away from his own presidential campaign.

Gore did state two years ago, long before Clinton even announced she would run in the race, that he had no problem supporting her campaign if she won the primary.

'I’m of course fully aware of the general expectation that she will run and that she’ll get the nomination,' said Gore.

'And if that happens, I certainly hope that she wins and I certainly hope that if she wins she’ll be an effective advocate on climate.'

One insider told Politico though that just because Gore might endorse Clinton it does not mean she is his top pick, saying that the former vice president is still angry about the Monica Lewinsky scandal and the impact it had on him as part of the Clinton administration.

'Some of the stuff that’s been plaguing the Clinton campaign … is the stuff he doesn’t like about serving with the Clintons,' said a veteran Democratic operative who worked for Gore in the past.

'My guess is he’ll endorse Hillary Rodham Clinton. But if he were to close his eyes and wish for a leader who he would want to lead the world it’s not where he would land.'