Former Secretary of State John Kerry said Sunday during an appearance on Face the Nation that he thinks former president Barack Obama should have enforced his 'red line' warning in Syria and thinks the United States paid a price as a result.

Kerry said he thought Obama was going to launch a missile strike in Syria in 2013 after the country attacked its own citizens with chemical weapons.

A year before the attack, Obama had warned Syrian president Bashar al-Assad that the use of chemical weapons would be a 'red line' that would be a 'game changer' for US involvement in Syria.

'I thought we were going to go forward. I thought that weekend was the weekend. I expected the phone call to be telling me that he had decided we were striking that night or whatever was going to happen, and it wasn't,' Kerry said on Face the Nation.

Former Secretary of State John Kerry (pictured) said on Face the Nation that he thinks Obama should have enforced his 'red line' warning in Syria

In 2012, Obama warned Syria that if it used chemical weapons that would be a 'red line' and that would be a 'game changer' for US involvement in Syria

'I put several ideas on the table. The president was not persuaded by my argument. I believed that we had several options we could have done at very low risk to be able to make it clear to Assad that when we had a ceasefire and when he said he was going to live by it, he had to live by it. And I thought we should have done that.'

Kerry said he thinks the US 'paid a price' because Obama did not stand by his warning.

'But we got the chemical weapons out, which was the objective,' he added.

Kerry, who wrote about Obama's inaction in his book Everyday is Extra, went on to say that although he doesn't agree with how the president handled it, he doesn't think it was a 'weak' moment for Obama.

Obama, however, changed course following Syria's attack on its own people with chemical weapons. Syrian president Bashar al-Assad is pictured during a May meeting in Russia

'I don't think it's fair in terms of the president quote 'being weak' because the president took a lot of very tough positions and did a lot of things that evidence strength and that showed a president who had a very clear moral compass as well as very clear, a very clear set of values and principles by which he knew he could protect our country,' Kerry said on Face the Nation.

When asked if he supported the way president Donald Trump handled Syria following its continued use of weapons, Kerry said he agrees with Trump using force but doesn't think it should have stopped there.

'I don't support just a one-off where you drop a few bombs and there's no follow-up diplomacy and no additional effort to try to use the leverage you get out of doing that,' he said. 'I thought that the president should have done that, President Trump should have done that.'