Iranian major general Soleimani was killed last month in a US drone strike in the Iraqi capital Baghdad ordered by Trump, bringing the entire Gulf region close to a full-blown conflict.
His comments came at the start of a five-day Gulf tour that had been thrown into doubt after Tehran responded to the attack on Qasem Soleimani by launching a barrage of missiles at bases hosting American troops in Iraq, prompting fears of all-out war.
His comments come hours after Iran launched missile strikes against two US military bases in Iraq in retaliation to the killing of its top commander General Qassem Soleimani.
The benchmark WTI jumped as much as 4.53 percent to $65.54 a barrel before settling down slightly after Iran unleashed its first response to the US assassination of military commander Qasem Soleimani.
The foreign ministry said it had submitted two letters to the UN and asked the Security Council to condemn the "assassination" of Iranian Major General Qasem Soleimani in an American drone strike on Baghdad
Supreme leader Ayatollah Ali Khamenei vowed "severe revenge" after a US drone strike Friday in Baghdad killed Qasem Soleimani
"The killing of Soleimani.... was an adventurist step that will increase tensions throughout the region," news agencies RIA Novosti and TASS quoted the foreign ministry as saying.
"There is no doubt that the great nation of Iran and the other free nations of the region will take revenge for this gruesome crime from criminal America," Rouhani said in a statement posted on the Iranian government website.
"Martyrdom was the reward for his ceaseless efforts in all these years," Khamenei said on his Farsi-language Twitter account in reference to Soleimani, also declaring three days of mourning.
The strike conducted in Iraq against Iran's Qasem Soleimani "went forward with no notification or consultation with Congress," House Foreign Affairs Committee chairman Eliot Engel said in a statement.