Syria: Consult Commons on arms sales Miliband urges PM
Ed Miliband has urged David Cameron to guarantee a Commons vote before any arms are sent to the Syrian opposition.
Raising the issue at Prime Minister's Questions, the Labour leader said a "substantive" vote was needed, with Parliament being recalled if necessary.
In response, Mr Cameron said MPs would "have a say". No 10 later said a vote would be held "when the time is right".
Speaking later in the US, Foreign Secretary William Hague said more had to be done to "save lives" in Syria.
After talks with his US counterpart John Kerry, Mr Hague said the level of repression by the Syrian government of President Bashar al-Assad "beggared belief" and reports of the use of chemical weapons were credible.
While the UK's focus remained on a diplomatic situation, he said the regime's actions were making this "more difficult".
The UK and France have led calls for more support for the official opposition in Syria, but MPs from all parties have warned of the dangers of escalating a conflict that has already claimed the lives of 80,000, and of strengthening extremist elements.
More than 80 Tory MPs have signed a letter urging the government to consult Parliament before any decision is taken.
Mr Miliband said the prime minister had put more energy into negotiations over lifting the EU arms embargo, which authorises the UK and other nations to supply arms if they so choose, than potential peace talks.
Citing the debate held last year on UK military support for the Libyan opposition, Mr Cameron said he believed in letting the Commons have a say on "all of these issues" and "it would be right in the future for that to happen".
Critics say British planes were already being scrambled when the Commons backed UK intervention in the Libyan uprising.
Mr Cameron added: "The point about lifting the arms embargo is to send a very clear message about our intentions and about our views to President Assad."
"But we have not made a decision to supply the Syrian opposition with weapons. As I said, we are giving them assistance, we are giving them advice and we are giving them technical help."
The prime minister also said he would be meeting Mr Putin in No 10 on Sunday, ahead of the G8 summit in Northern Ireland.
Russia is an ally of, and has sold arms to President Bashar al-Assad's Syrian government, and said last week it was "disappointed" by the EU ending its embargo on arms sales to the opposition.
Mr Cameron and Mr Putin held talks last month in the Black Sea resort of Sochi in Russia.
At the time, Mr Cameron said that although the two men disagreed on strategy, they agreed on the need to end the violence, prevent the growth of extremism and stop Syria "fragmenting".
Sunday's meeting was intended to "crank up the pressure" on all sides in the conflict, the prime minister said.
"We all want... a peace conference, a peace process and a move towards a transitional government," he said, while admitting there were differences on how to get there.
Speaking in Washington, Mr Kerry said the US was doing all it could to support the opposition to "change the (military) balance on the ground" but emphasised the need for a political solution.
Referring to the alleged use of chemical weapons, he said the government's actions had "challenged anybody's values and standards of human behaviour".
More than 80,000 people have been killed and 1.6 million have fled to neighbouring countries since the uprising against President Assad began in March 2011, according to the UN.