Iran says the hostile policies of US President Donald Trump are to blame for the rising prices of crude oil in international markets, rejecting his Wednesday attack against the Organization of the Petroleum Exporting Countries (OPEC) for the current supply situation.

Hossein Kazempour Ardebili, Iran's OPEC governor, emphasized that the sanctions that Trump had devised against Iran and Venezuela were largely to blame for high oil prices.

"You cannot place sanctions on two OPEC founder members and still blame OPEC for oil price volatility," he said in a statement to Reuters.

Kazempour Ardebili’s comments came in response to a Trump message in which he had accused OPEC of working to push up the prices.

"Oil prices are too high, OPEC is at it again. Not good!" he wrote in a post on Twitter.

Oil prices have risen by around 60 percent over the last year after OPEC and some non-OPEC producers including Russia arrived at an agreement in 2017 to reduce supplies, Reuters wrote in its report.

The price of Brent crude peaked in May at $80.50 a barrel, then pulled back, trading on Wednesday near $76 at barrel, partly in anticipation that the agreement may end.

OPEC will meet next week in Vienna, and producers are seen as likely to raise production, perhaps before the limits are due to sunset at year-end.

The oil supply agreement is set to continue through the end of 2018, but plans for its continuation were unclear. The calculus changed after Trump announced in May that the United States was pulling out of the 2015 deal that restricted Iran's nuclear program in exchange for the removal of sanctions.

Trump also said he would launch mechanisms to re-impose what he described as the “highest level of sanctions” against Iran.

The sanctions would include a universal ban on Iran over buying or acquiring US dollars as well as restrictions over purchases of crude oil from the country and investing in its oil sector projects.

The US move has put pressure on European and Asian clients to stop importing Iranian oil or doing business with the country.

This is expected to create a gap in supplies of above 2.7 million barrels per day of Iranian oil to international markets amid fears that prices could rise even higher.