MPs debate whether Britain should act on Syria crisis
UK politicians have debated how Britain should respond to the crisis in Syria, at an emergency meeting of parliament.
There's growing concern for the Syrian people, following last week's suspected chemical weapons attack.
MPs will vote on whether it would be right for the UK to join a possible military response, led by America.
But today's vote won't lead to any immediate action, as they've decided to wait for more evidence about the attack from United Nations investigators.
Mr Cameron said it's "highly likely" that the Syrian government was behind the attack.
He went on: "Britain should not stand aside. We should prepare ourselves for a strong international response."
Labour leader Ed Miliband said that he isn't against a military response - but that ministers must be clear on what could happen if Britain becomes involved.
Avoiding another Iraq
One reason politicians are divided over the issue is they want to avoid a repeat of the war in Iraq.
The invasion of Iraq, by British and American troops in 2003, was to try to overthrow the leader Saddam Hussein - who was believed to hold very powerful weapons. But these weapons were never found, and many people in Britain opposed the invasion.
It's for this reason that the Labour party wants "compelling evidence" from the United Nations that Syria's president, Bashar al-Assad, was behind the chemical attacks, before agreeing to a military response from Britain.
But Mr Cameron said that Iraq was "very different" and that Britain "must be sure to learn the lessons of previous conflicts".
Should Britain get involved at all?
MPs will now vote on whether it's right or wrong to get involved at all, and another decisive vote will take place once the UN has reported.
The head of the UN, Ban Ki-Moon, says that he expects a report from inspectors on Saturday.
President Obama has said that he has not yet decided what America's response should be - but if the US does get involved, it would be to say clearly to Syria's government: "Stop doing this".
America and Britain's governments both believe that President Assad is responsible for the chemical attack - but the Syrian government denies this, saying it was anti-government rebels.
UN inspectors are carrying out tests near the Syrian capital, Damascus, to see whether chemical weapons have been used there.
More than 300 people are reported to have died of poisoning from a suspected chemical attack last week.