Western foreign ministers are to meet to consider "all the options" for ending the current crisis in Syria, Boris Johnson has said.
Amid continuing air strikes on the beleaguered city of Aleppo, the Foreign Secretary said that the time had come to look at the "more kinetic options" – including military options.
But giving evidence to the Commons Foreign Affairs Committee, he said they had to be "realistic" about what was possible and that any intervention would require a coalition with the Americans - which could be some way off.
Mr Johnson told MPs that he had summoned a meeting of foreign ministers – including US Secretary of State John Kerry, as well as ministers from France and Germany – on Sunday to consider a new way forward in Syria and Iraq.
"Most people – I think including John Kerry – feel that the process of discussion with the Russians has basically run out of road," he said.
"On Sunday, we will be talking about all the options that we think are available to us and to the West. I am not going to pretend that there is any easy answer here, because there isn't.
"Most people, I think, are now changing their minds about this and they are thinking 'We can't let this go on for ever, we can't just see Aleppo pulverised in this way, we have to do something'.
"Whether that means we can get a coalition together now for more kinetic action now, I cannot prophesy, but certainly what most people want to see is a new set of options."
Following calls from MPs from both sides of House for the establishment of a no-fly zone during Tuesday's Commons debate on Syria, Mr Johnson stressed they had to be "realistic" about what it was possible to achieve.
"It is right now we should be looking again at the more kinetic options and the military options, but we must be realistic about how these in fact work and what is deliverable," he said.
"Certainly you can't do anything without a coalition with the Americans. I think we are still a pretty long day's march from getting that, but that doesn't mean that discussions aren't going on because they certainly are."
He added: "It is vital we do not raise false hopes. We know the difficulties and implications of a no-fly zone or no-bombing zone, no matter how easy these concepts may be made to seem.
"If there is more we can reasonably and practically do together with our allies, then of course we should consider these measures - and believe me that work is already going on."
Mr Johnson, who infuriated Moscow with his accusations that Russian forces are attacking Aleppo in support of the regime of President Bashar Assad, insisted he was not seeking a new cold war stand off.
But he said the actions of President Vladimir Putin represented a "serious problem" and that the West's stance on Russia had to remain "very, very tough".
"It is doing many, many terrible things, but I don't think that Russia today can be compared with the Soviet Union as I remember as a child. I don't think it is right to talk about a new cold war," he said.
"We have a very serious problem, but have to engage with Russia - we have to persuade the Russian government, we have to persuade Vladimir Putin, that there is another path for him and for his government," he added.
Asked whether sanctions on Russia in response to its actions in Syria were an option, Mr Johnson said: "The big anomaly in the whole issue of sanctions against Russia is that much of western Europe continues to take huge amounts of Russian gas.
"There are some European countries who see that's where the sanctions should go next. That would be very difficult because I think 50% of German gas supplies come from Russia. That's big stuff and that would be damaging to those economies as well as to Russia."
Downing Street confirmed that Sunday's meeting will be held in the UK, but a precise venue was not immediately available.
Theresa May will "weigh up very carefully" any military or other options put forward to end the crisis in Syria, the Prime Minister's official spokeswoman said.
"There is no change in the Government's position with regard to that (military action)," the spokeswoman said.
"Clearly when the Government and Parliament considered this before, there were concerns about a range of action.
"Since then, obviously the conflict has continued and we started taking action against Daesh.
"But I think the Prime Minister would weigh up very carefully any options that were put forward and the potential consequences of those.
"At the moment our focus is on bringing together partners, as I think the Foreign Secretary outlined at the committee.
"We will be gathering leaders in the UK this weekend to talk about what more we can do."
On Mr Johnson's assertion that discussions with Russia had "run out of road", the spokeswoman said: "He is talking about the difficulties that we have had - and when you co-sponsor a Security Council resolution that calls for the ending of the bombardment of innocent civilians and you see that vetoed by another permanent member of the UN Security Council, it is right to be questioning where do you take these discussions next."