Defence Secretary Philip Hammond said there was a "body of opinion within Cabinet who believes that we have to look at the welfare budget again", and that "we should be seeing welfare spending falling" as a result of rising employment levels.
He said the "first priority" for the Government should be "defending the country and maintaining law and order" and that further defence cuts were not possible while meeting stated security objectives.
I shall go into the spending review fighting the case for the defence budget on the basis that we have made very large cuts to defence, we've done that with the collaboration and co-operation of the military.
Any further reduction in the defence budget would fall on the level of activity that we were able to carry out - the idea that expensively bought equipment may not be able to be used, expensively employed troops may not be able to be exercised and trained as regularly as they need to be.
I am not going into the spending review offering any further reductions in personnel.
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It is hoped the 7,400-mile journey will become a cost-efficient and time-saving way of transporting trade between China and the UK.
The Prime Minister said Parliament will be given a binding vote on the final deal, but said the result will not stop Britain leaving the EU.
Officials from the train drivers' union Aslef will meet managers from Southern Railway, whilst the RMT will meet separately with Acas.