WASHINGTON, Aug 23 (Reuters) - The Pentagon has been quietly blocking Ukraine from using U.S.-made long-range Army Tactical Missile Systems (ATACMS) to strike targets inside Russia, limiting Kyiv's ability to employ these weapons in its defense against Moscow's invasion, the Wall Street Journal reported on Saturday, citing U.S. officials.Reuters could not immediately verify the report.The Reuters Daily Briefing newsletter provides all the news you need to start your day. Sign up here.The news came as U.S. President Donald Trump has grown more frustrated publicly over the three-year-old war and his inability to secure a peace deal between Russia and Ukraine.After...