Oil prices, which have risen on worries about Washington's possible withdrawal from the Iran agreement, are unlikely to take a leg higher even if the U.S. ultimately pulls out of deal, according to one expert. Markets have already factored in the possible effect of the U.S. re-sanctioning Iran, currently the third-largest oil producer in the Organization of the Petroleum Exporting Countries. "We've already seen that bullishness factored in over the past few weeks ... The markets have already reacted to the expectation of less supplies going forward," Alejandro Barbajosa, vice president at Argus Media, told CNBC's Nancy Hungerford. As a result, it will be difficult for oil prices to advance under current circumstances, Barbajosa said.

Oil prices declined in Asia trade on Tuesday, following a tweet from President Donald Trump that he will announce his decision on the Iran deal on Tuesday at 2 p.m. ET. The 2015 accord lifted economic sanctions on Iran in exchange for the country limiting its nuclear program and allowing regular inspections of its to atomic facilities. The United States agreed to those terms, and Iran does not appear to have violated the deal, but the Trump administration has said it wants to scrap the agreement. U.S. crude futures, which had topped the $70 per barrel mark in the last session for the first time since end-2014, had slid 1.2 percent to around $69.88. Brent crude futures were down 1.01 percent at $75.40.

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