Boris Johnson is heading up crisis meetings to consider the UK's response to Vladimir Putin's actions in Ukraine.
It comes after the Government announced new sanctions on key Russian figures and businesses after President Putin recognised two breakaway regions of eastern Ukraine as independent states.
Latvia's foreign minister said sanctions are effective in the long term in response to Vladimir Putin's actions in Ukraine.
READ MORE: Martin Lewis shares how to get your NHS prescriptions cheaper
Edgars Rinkevics told BBC Radio 4's Today programme: "In a short perspective, yes of course - sanctions cannot stop Russia from invading Ukraine or from doing what they did, but in the long term, especially, those sanctions are related to technology transfers, to financial sector, they actually would slow down developmental pressure and that would actually repeat some kind of Soviet Union experience.
"That at one given time in history, Soviet Union simply collapsed."
At the Cobra committee, Boris Johnson will be briefed on the latest intelligence after Mr Putin ordered his troops to carry out 'peacekeeping' duty in the Donetsk and Luhansk regions.
UK's ambassador Dame Barbara Woodward said this has "brought us to the brink", warning that the country's actions "will have severe and far-reaching consequences."
Dame Barbara Woodward said: "The humanitarian impact will be terrible on civilians fleeing the fighting. We know that women and children will suffer most."
She added: "Russia has brought us to the brink," she said. "We urge Russia to step back."
The Kremlin said Russian forces will 'maintain peace' in eastern Ukraine.
But Boris Johnson said the decision from Mr Putin to recognise Donetsk and Luhansk was an "ill omen" and a flagrant breach of international law.
No 10 has said the Cobra meeting will co-ordinate the UK response and agree a "significant package of sanctions to be introduced immediately."
Following the meeting the Prime Minister will have a string of calls with other world leaders and will update MPs on the sanctions package at around 12.30pm.
Cabinet minister Sajid Javid said: "We are waking up to a very dark day in Europe and it's clear from what we have already seen and found out today that the Russians, President Putin, has decided to attack the sovereignty of Ukraine and its territorial integrity."
The Health Secretary told Sky News: "We have seen that he has recognised these breakaway eastern regions in Ukraine and from the reports we can already tell that he has sent in tanks and troops.
"From that you can conclude that the invasion of Ukraine has begun."
Receive newsletters with the latest news, sport and what's on updates from the Liverpool ECHO by signing up here
