Global crude oil prices fell again on Friday, putting an end to expectations of a third straight weekly increase despite continued tensions between the United States and Iran.

Brent crude futures for September fell 25 cents, or 0.3%, to $89.45 per barrel. US West Texas Intermediate (WTI) crude also declined 22 cents, or 0.3%, to $83.31 per barrel.

On a weekly basis, Brent was down around 5.3%, while WTI recorded a decline of about 4.3%.

US-Iran tensions remain

The decline came despite growing uncertainty surrounding relations between Washington and Tehran.

Reports said US President Donald Trump's administration is not currently interested in restoring a June understanding with Iran, making efforts to restart negotiations more difficult.

Washington has also said it is not holding direct talks with Tehran, while several countries continue diplomatic efforts to bring both sides back to negotiations.

New sanctions add uncertainty

The United States has imposed additional sanctions on Iran, describing them as among its toughest measures against the country.

Iran has rejected the sanctions as hostile and inhumane, arguing that such measures have lost their effectiveness.

Wider geopolitical risks

Oil markets are also watching tensions surrounding Russia and Ukraine. Moscow has warned that British military targets could become targets if Ukraine uses British-supplied long-range cruise missiles against Russian territory.

Meanwhile, Trump has said Russian President Vladimir Putin would not attack a NATO member, playing down some concerns over a possible wider conflict.

The latest oil price movement highlights how geopolitical developments and changing expectations around supply and demand continue to influence global energy markets.