World oil prices climbed Friday on the back of the weaker dollar, with further support stemming from worries over the nuclear standoff between the West and Iran, dealers said.
New York's main contract, West Texas Intermediate (WTI) crude for delivery in July added 27 cents to $90.93 a barrel
Brent North Sea crude for July gained 42 cents to $106.97 a barrel in early London afternoon trade.
"Crude oil prices are trading in modest positive territory, supported by some profit taking in the dollar which has pressured the US currency lower," said Sucden analyst Jack Pollard.
"The euro's relative strength, following a terrible week for the currency, seems to be underpinning a modicum of risk appetite but we do not expect it to hold."
The weaker greenback makes dollar-priced oil cheaper for buyers using stronger currencies and this tends to boost prices.
Investors remain anxious about the potential departure of Greece from the eurozone, and the possible repercussions for other fiscally-challenged nations like Italy and Spain.
Crude futures had risen on Thursday after European leaders reaffirmed their desire to see Greece stay in the euro, amid eagerly-awaited talks over Tehran's disputed nuclear programme.
Iran and six world powers ended two days of "very intense" nuclear talks in Baghdad on Thursday with little to show except an agreement to meet again next month in Moscow, on June 18-19, after sharp disagreements over the way forward.
EU foreign policy chief Catherine Ashton had on behalf of the P5+1 -- Britain, China, France, Russia and the United States plus Germany -- laid out a new package of proposals that appeared to alarm the Iranians.
These reportedly included Iran suspending enrichment of uranium to 20-percent purities -- for the P5+1, the most worrying part of Tehran's activity and the crunch issue, since it shortens the theoretical time needed to develop the bomb.
But the P5+1 offer went down badly with Tehran since in return it did not offer the relief from crippling sanctions sought by Iran.
Reflecting official thinking in Tehran, state media ran reports slamming the package, with the IRNA news agency calling it "outdated, not comprehensive, and unbalanced."
Ashton said in her closing news conference that Iran had "declared its readiness to address 20-percent enrichment" but she did not elaborate and also made no mention of sanctions.
Commerzbank analyst Carsten Fritsch added that oil prices were winning support from the lack of a breakthrough at the talks.
"The two days of nuclear talks ... came to a close yesterday without producing any concrete results," said Fritsch.
"Iran continues to insist on its right to enrich uranium, while the West makes abandonment of the enrichment programme a condition for the lifting of sanctions.
"Ahead of the talks there had been hopes of a breakthrough. Now that these hopes have not been fulfilled, part of the risk premium may return, which would argue against any further fall in the price of oil," he added.
Earlier this week, New York crude had slumped to a six-month low as heightened concerns over the eurozone debt crisis propelled the dollar to a 22-month peak against the euro.
New York crude tumbled on Wednesday to $89.90 a barrel -- the lowest level since October -- while Brent oil touched a five-month nadir.
Investors had shunned risky assets after the former Greek prime minister warned that Athens might leave the eurozone.