It is “morally indefensible” for Britain to rely on other countries to tackle the so-called Islamic State in Syria, Michael Fallon has said.
The defence secretary told BBC News he was appealing to MPs to reconsider the case for airstrikes.
It comes after a Russian passenger plane crashed in Egypt’s Sinai desert last Saturday, which the UK government suspects was caused by a bomb.
In 2013, MPs rejected possible UK military action in Syria.
The vote two years ago was on potential airstrikes against the regime of President Bashar al-Assad, amid reports he had used chemical weapons, rather than militants from Islamic State (IS or ISIL).
The government is now making the case for Islamic State to be targeted, given its links to attacks on Western targets around the world, including the killing of 30 British holidaymakers in Tunisia in June.
The four-year civil war in Syria has ground to a stalemate, with President Bashar al-Assad’s regime, so-called Islamic State, an array of Syrian rebels and Kurdish fighters all holding territory.