London, July 8 -- Crude stocks tumbled sharply on Wednesday after US President Donald Trump declared that the ceasefire with Iran was effectively "over" and described further negotiations with Tehran as "a waste of time," leading to surging prices amid fears of renewed conflict and closure of the Strait of Hormuz.

Brent crude, the global benchmark, climbed 6.3% to $78.80 a barrel, while US benchmark West Texas Intermediate (WTI) rose 6.4% to $75 a barrel.

The rally reversed a recent decline in oil prices that had seen WTI fall below $70 a barrel, close to levels recorded before the outbreak of the Iran war in late February.

The Dow Jones Industrial Average fell 479 points, or 0.9%, to 52,446, while the S&P 500 declined 0.4%, and the tech...