* "Inaction and indifference are not options" - Cameron
* Discussion on EU arms embargo to continue in coming weeks
By Justyna Pawlak and Peter Griffiths
BRUSSELS, Dec 14 (Reuters) - All options are on the table to support the Syrian opposition fighting President Bashar al-Assad, European Union leaders said on Friday, raising the possibility that non-lethal military equipment or even arms could eventually be supplied.
In their strongest statement of support for the Syrian opposition since the uprising began more than 20 months ago, EU leaders instructed their foreign ministers to assess all possibilities to increase the pressure on Assad.
Britain's David Cameron pushed for an early review of the arms embargo against Syria to potentially open the way to supply equipment to the rebels in the coming months, but Germany and others were more reluctant and blocked any quick move.
But there was widespread agreement that whatever action can be taken under current legislation should be pursued, and the arms embargo would still be reviewed at a later stage.
"I want a very clear message to go to President Assad that nothing is off the table," Cameron told reporters at the end of a two-day EU summit. "I want us to work with the opposition ... so that we can see the speediest possible transition in Syria.
"There is no single simple answer, but inaction and indifference are not options."
Officials said that Britain and France were keen for further discussion on lifting the arms embargo, to open the way for non-lethal assistance, at least initially.
That could be discussed as soon as Jan. 28, when EU foreign ministers will hold their next meeting in Brussels.
But Germany Chancellor Angela Merkel was far more cautious than Cameron, saying it was too soon to change the arms embargo.
"We are all convinced that there must be a political change in Syria, that the future of Syria is without Assad," she told reporters. "If it comes to a change of power and departure of Assad, then there must be a respect of human rights and protection of minorities."
But when it comes to arms or assistance with non-lethal equipment, she said it had not explicitly been discussed at the summit, saying it would be left up to foreign ministers.
"The foreign ministers are to discuss how to help the opposition ... Nothing has been decided as far as a loosening of the arms embargo goes," she said.
The EU's support for the Syrian opposition comes amid reports of gains for rebels fighting Assad's forces. Even Russia - an ally and arms supplier to Assad - has conceded there is the possibility of a rebel victory.
On Monday, EU foreign ministers had moved closer towards full recognition of the opposition Syrian National Coalition (SNC), after they met leader Mouaz Alkhatib in Brussels.
Pushed by Britain, the bloc decided in late November to review sanctions on Syria every three months instead of every year as previously, in order to make it easier for EU countries to equip the rebels.
The current embargo on the supply of arms to the country was imposed to prevent the flow of weapons to Assad's forces. The new, shorter review period will allow the EU to look at amendments that might allow the supply of non-lethal equipment to the rebels.