Donald's Trump's spokeswoman has claimed Hillary Clinton and Barack Obama were to blame for the 2004 death of Muslim soldier Humayun Khan - despite it occurring before they came to power in 2009.

Katrina Pierson made the comments as Mr Trump's row with the parents of the slain US soldier, who spoke at the Democratic National Convention, continued to escalate.

In an interview with CNN, Ms Pierson said: 'Donald Trump never voted for the Iraq War. Hillary Clinton did and then she didn't support the troops to have what they need.

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Trump campaign spokeswoman Katrina Pierson during the interview on CNN

'It was under Barack Obama and Hillary Clinton that changed the rules of engagement that probably cost his life.

'So I don't understand why it is so hard to understand why Donald Trump was confused about why he was being held responsible for something he had nothing to do with while Hillary Clinton had everything to do with while Hillary Clinton had everything to do with.'

In 2004, Mrs Clinton was US Senator for New York, becoming Secretary of State in 2009, while Mr Obama was then a state senator in Illinois.

CNN host Wolf Blitzer later issued a statement after the interview, telling viewers the death occurred under George W. Bush's presidency.

'I just want to fact check that,’ he said.

Ms Pierson is a spokesperson for Donald Trump's campaign

The exchange came as Ms Pierson questioned why Mr Trump was expected to apologize to the Kahn family.

President Obama yesterday challenged Republican leaders to withdraw their support for their candidate over his attacks on the Khan family.

‘The Republican nominee is unfit to serve as president and he keeps on proving it,’ he said.

'The notion that he would attack a Gold Star family that made 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's woefully unprepared to do this job.'

Mr Pierson said of whether Mr Trump had apologised: 'I think he has apologized by honoring the soldier’

New Jersey Governor Chris Christie distanced himself from the remarks by his ally Mr Trump, saying the death gave the couple the right to say whatever they want.

The candidate’s son, Eric Trump, defended his father and claimed that he had already apologized to the Khans.

Appearing on CBS, Eric Trump said: ‘He has (apologized) by calling them a hero,’ Eric Trump said.