U.S. Secretary of State Mike Pompeo said Soleimani was planning attacks on U.S. facilities and workers in Iraq, Lebanon, Syria and other countries.
A reprisal attack by Iran could send oil prices as high as $100 as global crude supply could be threatened.
"Nevertheless, heightened tensions in the region involving Iranian-backed forces may introduce a certain geopolitical risk", they added.
Already, Brent crude price is $9 above Nigeria's crude oil budget benchmark.
"The market is trying to assess whether we'll see a supply disruption, if any", said Andy Lipow, president of consultants Lipow Oil Associates.
"The American action was a reaction to a series of military provocations for which Iran is responsible", said Demmer.
Iraqi officials said the evacuation would not affect oil operations, production or exports from the country, the second-biggest producer in the Organization of the Petroleum Exporting Countries (OPEC) with output of about 4.62 million barrels per day (bpd), according to a Reuters news agency survey of OPEC output. About 20% of oil traded worldwide goes through the Strait of Hormuz, where the shipping lane is only 3 kilometers (2 miles) wide and tankers have come under attack this year.
The U.S. index futures are indicating a lower open in early Friday trading.
All oil fields across the country were operating normally and production and exports were not affected, Iraq's Oil Ministry said in a statement.
In the longer term, the rise in crude oil prices could be limited by the fact that the energy market is flush with oil while demand has softened as major economies have slowed. US crude prices increased about the same. "And, we still expect an oversupplied oil market in 2020".