Oil prices fell 5% on Monday, after U.S. President Donald Trump said Iran was "seriously talking" with Washington, signalling de-escalation with an OPEC member to ease supply disruption concerns. Brent crude futures were down $3.63, or 5.2%, at $65.69 per barrel at 0920 GMT. U.S. West Texas Intermediate crude fell $3.60, or 5.5%, to $61.61 per barrel. Brent and WTI fell after posting their biggest monthly increase since 2022 in January, as risks of a military strike on Iran receded after Trump's weekend comments. Brent gained 16% in January, while WTI rose by 13%.