PARIS/FRANKFURT, June 15 (Reuters) - ECB President Christine Lagarde on Monday welcomed news of a U.S.-Iran ceasefire, saying it could help reopen the Strait of Hormuz, although fellow policymaker Joachim Nagel cautioned it would bring no immediate relief to high euro zone inflation. U.S. and Iranian officials said overnight they had reached an agreement to end their war and reopen the Strait, a gateway for energy shipment, in a preliminary pact that sent oil prices falling and curbed bets on ECB rate hikes.