"Over the course of the next month we are going to be deploying British service personnel to provide advice and a range of training, from tactical intelligence to logistics to medical care, which is something else they have asked for," Cameron told a parliamentary committee.
"And we'll be developing an infantry training programme with Ukraine to improve the durability of their forces. This will involve a number of British service personnel.
"They will be away from the area of conflict, but I think this is the sort of thing we should be helping with."
The prime minister repeated that Britain would not supply lethal equipment to Ukrainian government forces.
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"The reason for not going further is we don't believe fundamentally there is some military solution to this issue," Cameron said.
"There needs to be a diplomatic solution which I think should be enabled by sanctions and pressure and the economic weight of Europe and America."
Foreign ministers from Ukraine, Russia, Germany and France called today for a total ceasefire in eastern Ukraine at a meeting in Paris, as Kiev accused Moscow and pro-Russian rebels on the ground of torpedoing a nine-day-old truce.
"We shouldn't be too precious about not being involved in every different set of negotiations," he said.
"There is no point endlessly obsessing about whether or not you are in the room. We have a very clear role when it comes to Ukraine.