European natural gas prices plunged at opening on Monday after U.S. President Donald Trump said he had called off a planned attack on Iranian energy sites and talks on a deal would begin this week. Europe’s benchmark natural gas prices, the Dutch TTF Natural Gas Futures, sank by 4% at the start of trade on Monday, following the 5% slump in oil prices amid renewed hopes that the U.S. and Iran are looking for a return to diplomacy. However, natural gas prices eased their losses mid-day as Europe faces another heatwave that boosts electricity…