REUTERS/Evelyn HocksteinWASHINGTON/DUBAI - US President Donald Trump said on Monday that talks with Iran were under way, warning that it was a "last chance" for Tehran to sign a good deal to end the five-month-old war, but Iran denied that any negotiations were being held or planned. Earlier on Monday, Iranian Foreign Ministry spokesman Esmail Baghaei said no negotiations with the United States were taking place and no meetings were scheduled. The only talks under way, he said, were discussions with Oman over management of the Strait of Hormuz. "'The United States Wall of Steel!' So far the United States has failed to compel Iran to relinquish its grip on the waterway, sending global oil prices higher and pushing up politically sensitive gasoline prices in the United States.