Pentagon Press Secretary General Patrick Ryder:

Pentagon Press Secretary General Patrick Ryder: [In Vietnam, Putin said Russia was going to change its first-strike nuclear doctrine. Are you taking this seriously or is this just saber rattling?] “At the moment there is nothing that would require an adjustment to our military-strategic doctrine. And this is not the first time we have heard about the careless rattling of nuclear weapons. It is, of course, irresponsible for countries with this kind of potential to make such statements. Let me return to what I said earlier: our priority is security and stability - not only in the region, but throughout the world. So we'll continue to focus on that.” Source: Russian Head