The possibility of Vladimir Putin being turned into an international pariah has moved a step closer after the US admitted it may impose sanctions against the Russian president.

A State Department spokeswoman admitted on social media that the US could make the move to punish Mr Putin over his invasion of Crimea.

Asked last night on Twitter if such a move was possible, the aide, Jen Psaki, replied in the affirmative, before adding it was important "to lay out consequences" of his actions.

She further spelled out that the US was "able to sanction people, companies, and sectors. Goal not sanctions. Goal de-escalation. Range of officials under consideration. Plenty to sanction before we would discuss President Putin".

The US has imposed visa bans and assets freezes on several Russian officials and lawmakers deemed to have been involved in Russia's annexation of the region from Ukraine last month, and it has targeted businessmen with ties to Putin.

It has warned of further sanctions, including measures affecting entire economic sectors, if Russia does not follow through on an agreement reached last week by Russia, Ukraine, the US and the European Union in a bid to ease the crisis.

Mr Putin has claimed that Russia is not interfering in eastern Ukraine, where pro-Russian separatists have seized buildings. Ms Psaki tweeted: "Putin rhetoric doesn't match facts on ground."

Meanwhile, Secretary of State John Kerry urged Russian Foreign Minister Sergei Lavrov in a phone call to help implement the agreement.