Avoidance of "automaticity", a system where there is an automated retaliation in the form of a nuclear strike, and the need for new low-yield nuclear weapons are among the highlights of the Nuclear Posture Review (NPR) of the USA government released over the weekend.
Regarding China, in addition to describing the Asian country as an adversary, Washington pointed out that it is ready to prevent Beijing from taking advantage if it uses that military technology in Asia or accepts its use in a lesser scale.
The report said the United States strategy for China is created to "prevent Beijing from mistakenly concluding that it could secure an advantage through the limited use of its theatre nuclear capabilities or that any use of nuclear weapons, however limited, is acceptable".
"We hope that the United States will abandon its Cold War mentality", Mr Ren said.
The NPR states that both China and Russian Federation have "added new types of nuclear capabilities to their arsenals, increased the salience of nuclear forces in their strategies and plans, and engaged in increasingly aggressive behaviours, including in outer space and cyberspace".
China's nuclear arsenal is relatively small, estimated by the Stockholm International Peace Research Institute at just 270 warheads compared with 6,800 for the US.
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A Syrian militant in the area told The Associated Press that the Russian pilot was shot and killed when he resisted capture. The YPG controls much of the territory along the border and an uninterrupted strip from Manbij to the Iraqi border.
The US military wants to revamp its nuclear arsenal and develop new low-yield atomic weapons, largely in response to Russian actions in recent years, the Pentagon said. China has also long maintained it will never allow first use of its atomic weapons.
Iran's foreign minister claimed it brought the world "closer to annihilation".
"That is why precisely we in Europe must begin new initiatives for arms control and disarmament".
The doctrine notes that these activities are not intended at being employed for nuclear warfare, however, they are aimed at raising the U.S. nuclear threshold to ensure that the country's potential adversaries perceive no possible advantage in nuclear escalation.
"The United States would only consider the use of nuclear weapons in extreme circumstances to defend the vital interests of the United States, its allies and partners", according to the NPR.
Low-yield nuclear weapons, while still devastating, have a strength of less than 20 kilotons.
Iran's nuclear deal, reached with six world powers, lifted some worldwide sanctions in exchange for curbs to its nuclear programme.