Brent crude fell more than 6% on Monday morning, retreating from its highest close since March, as regional mediators headed to Tehran and US President Donald Trump weighed a deal with Iran, while investors braced for a week packed with central bank decisions and earnings reports.Oil prices tumbled on Monday morning as diplomatic efforts to calm the Iran war gathered pace and US President Donald Trump said he was weighing a deal with Tehran.Brent, the global oil benchmark, fell more than 6% from...