By Robert HarveyLONDON, Jan 29 (Reuters) - Brent oil futures prices jumped on Thursday, hitting a four-month high on rising concerns of a possible U.S. military attack on ​Iran, OPEC's fourth-largest producer, with output of 3.2 million barrels per day. Brent crude futures were up $1.52, or 2.22%, to $69.92 a barrel at 1210 GMT. At its intra-day peak, Brent traded as high as $70.35 a barrel, its highest since late-September. U.S. West ⁠Texas Intermediate crude was up $1.48, or ‌2.34%, to $64.69 a barrel. WTI futures earlier topped $65 a barrel, also a four-month high.