The Government remains committed to building parliamentary support for RAF air strikes against Islamic State (IS) in Syria despite Russia's intervention in the conflict, Defence Secretary Michael Fallon has said.
Following talks in London with US defence secretary Ash Carter, Mr Fallon said Russian strikes in support of President Bashar Assad risked making "a grave situation even worse".
However he made clear that ministers would not be deterred from seeking support for a new Commons vote for British warplanes to join the US and other coalition aircraft in attacking IS - also referred to as Isil - in Syria as well as Iraq.
US Defense Secretary Ash Carter has said Russia's actions in Syria are "risky" and "will only inflame the civil war".
He added that Nato "stood strong" against Russia in Ukraine and this "strengthened posture".
ITV News Correspondent Dan Rivers is at the news conference in London.
Defence Secretary Michael Fallon has said Russian behaviour "threatens our allies".
He also announced £70m is to be invested in the next five years to drive innovation in new technology for the military.
He is speaking at a press conference in London along with US Defence Secretary Ash Carter.
Mr Fallon said: "Aggressive Russian behaviour continues threatening our allies in Europe."
ITV News Correspondent Dan Rivers is at the news conference.
David Cameron has cofirmed that Michael Fallon is to remain Defence Secretary
Defence Secretary Michael Fallon says he has no regrets on his personal attack on Ed Miliband and called it part of the "rough and tumble of politics".
Fallon has been criticised by party leaders for saying the Labour leader "stabbed his brother in the back" over the pair's 2010 leadership contest and would do the same to Britain to get into power.
Asked today during a visit to the Royal United Services Institute if he regretted the comments he said "absolutely not" and said that voters have the right to know who was leading Labour.
ITV News Deputy Political Editor Chris Ship was there:
The Defence Secretary has praised Britain's armed forces for their work in fighting Islamic State (IS) extremists during a visit to Cyprus.
Michael Fallon told the 400 service personnel based at RAF Akrotiri he was "proud" of their role in helping the Iraqi government defend itself against the threat of IS.
"While this fight will take time, the coalition's air strikes are having a direct effect in supporting Iraqi ground operations against IS," Fallon said.
"In the north, areas around Mount Sinjar have been retaken, bringing relief to the local Yazidi population and applying pressure to IS forces in Mosul. In the south, Iraqi forces operations are beginning to push back ISIL."
Britain will not deploy combat troops to Ukraine, which is fighting pro-Russian separatists along its eastern flank, Michael Fallon told parliament.
"We are not deploying combat troops to Ukraine and will not do so," Fallon said when asked whether the deployment of military personnel would provoke so-called mission creep.
Britain is preparing to send 75 troops and military staff to help with training and is considering more Ukrainian requests for help, the Defence Secretary added.
Mr Fallon confirmed British personnel will be based around Kiev or in western Ukraine, away from the fighting in eastern Ukraine.
Supplying weapons to Ukraine would escalate the conflict with pro-Russian separatists, Defence Secretary Michael Fallon has said.
The defence secretary backed fresh diplomatic efforts by the leaders of France and Germany to bring an end to the deadly conflict, which has claimed the lives of more than 5,000 people since April.
He also warned that Britain may have to update its nuclear deterrent in response to the Russian modernisation of its nuclear weapons.
Russian military planners may have "lowered the threshold" for the use of nuclear weapons, he added.