Brent and U.S. WTI crude oil prices fell to their lowest levels in almost six years on Tuesday as a big OPEC producer stood by the group's decision not to cut output to tackle a glut in the market.
A diplomatic push by Venezuela and Iran for an OPEC oil output cut has failed to soften the refusal of the group's Gulf members to do so for now, delegates said on Monday.
Iran's supreme leader Ayatollah Ali Khamenei told Venezuela's president on Saturday he backed coordinated action between Tehran and Caracas to reverse a rapid fall in global oil prices which he described as a "political ploy hatched by common enemies".
Oil prices sank to fresh 5-1/2-year lows on Tuesday, extending losses after a 5 percent plunge in the previous session as worries over a global supply glut intensified.
Venezuelan President Nicolas Maduro said on Sunday he will visit China and several unspecified OPEC countries during a week-long tour meant to improve the South American nation's finances, which have been weakened by tumbling crude prices.
U.S. crude and Brent futures dropped to fresh 5-1/2-year lows on Monday as worries about a surplus of global supplies amid weak demand continued to drag on oil markets.
Brent crude LCOc1 reversed early gains to trade near $57 a barrel on Friday, as the glut of oil that has halved prices since June overshadowed investors repositioning at the start of the year for an eventual recovery.
Falling world oil prices will hurt countries across the Middle East unless Saudi Arabia, the world's biggest crude exporter, takes action to reverse the slump, Iran's deputy foreign minister told Reuters.
Oil prices fell on Wednesday to a 5-1/2-year low and ended with their second-biggest annual decline ever, down by half since June under pressure from a global glut of crude.
President Nicolas Maduro vowed on Tuesday to reform Venezuela's Byzantine currency controls in early 2015 as part of a six-month plan to shake Venezuela out of recession, but foes accused him of incompetence and inaction.
Crude oil prices on tumbled on Monday, with global grades settling down more than $1 a barrel after an early rally fizzled and prices fell to their lowest levels since May 2009.
Russia's economy shrank sharply in November and the rouble resumed its slide on Monday as Western sanctions and a slump in oil prices combined to inflict the first contraction in GDP since the global financial crisis.
Oil prices rose on Monday, after dropping for the past two sessions, as escalating clashes in Libya stoked worries about supply from the OPEC member.
A big oil price slide will hurt Iran's attempts to rescue battered living standards, but economic pain is unlikely to soften its stance in nuclear talks or end aid to allies such as Syria, matters seen by its ruling clerics as strategic priorities.
Arab OPEC producers expect global oil prices to rebound to between $70 and $80 a barrel by the end of next year as a global economic recovery revives demand, OPEC delegates said this week in the first indication of where the group expects oil markets to stabilize in the medium term.