Russia's occupation of Crimea will prove a "big miscalculation" in the long-term, William Hague said as he sought to keep up pressure for a diplomatic solution.
The Foreign Secretary conceded that none of the sanctions being threatened by the West could remove Moscow's military forces from the Ukrainian peninsula.
But he said there would be "very significant" consequences for Russia's future global influence if it refused to enter talks with Kiev over the stand-off.
The population of the key strategic region is due to vote in a referendum on becoming part of Russia in a week's time after pro-Russian forces seized control of key military and other facilities.
Hague dismissed Vladimir Putin's claims that the insignia-less troops are local fighters not Russian personnel - though he declined to say directly that the Russian president was lying.
The Kremlin "clearly had a well-rehearsed plan to move militarily" into the region which it was forced to hurriedly implement on the ousting of pro-Russian Ukrainian president Victor Yanokovich, Hague said.
But despite criticism of the failure of the EU to impose sufficiently stringent sanctions on Moscow, Hague insisted there was no "tacit acceptance" of the takeover in the Crimea.
"It would be wrong to conclude that Russia has won in some sense. I think this will turn out over time to be quite a big miscalculation," he told BBC1's Andrew Marr Show.
"The long-term consequences will be very significant for Russia.
"European nations will, if no solution to this can be found, recast their approach to energy and economic links to Russia over time.
"The long-term effect will be to unite Ukraine more against Russian domination of their affairs and to recast European policies in a way that will reduce Russian leverage over Europe."
He went on: "None of the measures we can propose remove Russian forces from the Crimea. Nobody is proposing a military conflict between the West and Russia.
"But some of the diplomatic and other costs to Russia of this are serious and need to be taken seriously in Moscow."
Hague said he would later today have more talks with US secretary of state John Kerry on the latest developments as Western allies seek to secure direct talks between Moscow and Kiev.
The Kremlin refuses to recognise the legitimacy of the interim Ukrainian government and the Russian parliament has backed the Crimean legislature's decision to rejoin Russia subject to the backing of its majority-Russian population in the proposed March 16 vote.
The European Union has suspended talks with Moscow on visa liberalisation and threatened asset bans and travel freezes on Russian officials if there is no rapid progress to a diplomatic solution.
Labour says the position is too weak and called on the EU to be "more explicit about the real costs and consequences for Russia if it fails to de-escalate this crisis".
Fears over the economic consequences for Europe's fragile economies and the dependence on Russian gas have thwarted agreement on a tougher response.
Hague said that there was "clearly an increased case for American gas exports to Europe" and other measures to reduce reliance on Russian energy supplies.
Discussions were under way with Washington about that issue, he said.
Asked if Putin was lying about the presence of Russian troops, he said: "There clearly are Russian troops in Crimea.
"All the evidence is that they are. There is no plausible explanation of where else they have come from.
"They have taken possession of the Crimea. But I would argue that it would be in Russia's interest, faced with these short-term and long-term consequences of this action, to enter into a diplomatic process with Ukraine, supported by other nations."
Shadow foreign secretary Douglas Alexander said Europe needed to be "more explicit about the real costs and consequences for Russia if it fails to de-escalate this crisis".
He said the EU's failure to translate condemnation into concrete action risked emboldening the Kremlin and increasing the risk of escalations elsewhere in the world.
Writing in the Independent on Sunday, he said there should be a "graduated hierarchy of diplomatic and economic measures that could help effectively pressure Russia into changing course".
Negotiations on Russia's application to the Organisation for Economic Co-operation and Development (OECD) should be suspended, he suggested.
A "clear deadline for progress" should be set after which threatened asset freezes on Russian officials suspected of involvement were implemented.
The freezing of bank accounts belonging to 18 Ukrainians suspected of misappropriating state funds - including that of ousted president Victor Yanukovich - should be extended to Russian officials.
And he said the G7 countries "should seek agreement to suspend Russia from the group until it changes course" if there was no rapid progress.
They have already suspended preparations for the next G8 summit due to be hosted by Russia - which appears unlikely to go ahead.
"As well as the immediate security threats to the Ukraine, Russia's recent actions have also reaffirmed the existence of a geopolitical fault line that the West ignores at its peril," Alexander said.
"So now, over a week after Russian troops took effective control of the Crimea, the West must raise the costs to Putin for his reckless actions," he wrote.
"On the one hand, we must be clear that we want to see an inclusive government in Kiev, with protection for the rights of the Russian minorities within the Ukraine and guarantees that the EU Association Agreement does not preclude continuing trade relations between Ukraine and Russia.
"On the other, Europe must be more explicit about the real costs and consequences for Russia if it fails to de-escalate this crisis."
Prime Minister David Cameron will continue a round of discussions with fellow leaders of G7 countries when he meets German Chancellor Angela Merkel at an event in Hanover this evening.
Germany depends on Russia for around 40% of its gas supplies and business leaders there have been pressing hard against trade sanctions.
Former United Nations deputy secretary-general Lord Malloch-Brown said Europe had a duty to protect the Ukraine from Russian aggression, as he said the crisis was a "wake-up call for European defence spending".
Speaking on Sky's Murnaghan programme, he said: "On the Baltic states there is no equivocation, we have a treaty obligation to protect them and to make sure that this isn't some sort of creeping 1939.
"This will be a wake-up call for European defence spending, which has been dropping considerably because of this kind of economic crisis.
"Don't get me wrong, there needs to be real robustness to the response, but you come back to this point that Putin views London and Europe more generally as a little bit craven, willing to take Russia's money, willing to bank it, you know, do the rest for it, apologise and excuse it and wash it and launder it, if you like.
"And we've got to demonstrate that if we are going to be a haven for people from around the world, they have to live by our rules and laws. And that, equally, if there are countries abroad that break those international laws, there are treaties, there are consequences."