Russia warns West's increasing sanctions could end cooperation on Syria, Iran

Russia has warned the US that any tightening of sanctions on its economy would damage bilateral cooperation on some of the world's biggest geopolitical issues.

The warning comes after US lawmakers passed a bill that paved the way for the US to send increased military aid to Ukraine and to impose further economic sanctions on Russia.

US President Barack Obama subsequently signed off on tougher sanctions against Crimea, annexed by Moscow from Ukraine in March 2014.

Those penalties were designed to prevent Western businesses from investing in the Black Sea peninsula. The international payment system Visa shut off its Crimean banks on 26 December as a result of the latest sanctions.

Moreover, the Russian economy has suffered dire fortunes in 2014, with the government expecting a recession in 2015. Primarily driven by falling oil prices, Western sanctions have nonetheless contributed to the dire business sentiment in the country.

"The actions by the United States are putting in doubt the prospects of bilateral cooperation on solving the situation around the Iranian nuclear programme, the Syrian crisis and other acute international problems," the Russian foreign ministry said in a statement.

"As Washington could have seen previously, we don't leave such unfriendly acts without an answer."

Russia's use of the term "unfriendly act" points to an escalation in the anti-West attitude of the Russian government. In diplomatic language, it refers to actions by a hostile country that will likely lead to war.

Russian President Vladimir Putin has links with embattled Syrian President Bashar al-Assad, while relations between Moscow and Tehran remain strong.

World powers are in the middle of negotiations with Iran over the future its nuclear programme, offering to remove economic sanctions on the country if it makes good on assurances that it is not seeking to build a nuclear weapon.

Meanwhile, Assad stands accused of committing human rights abuses and using chemical weapons against his country's citizens in a bid to defeat opposition groups in the Syrian civil war.