And the UK's National Security Adviser, Sir Stephen Lovegrove, warned of the "pace and scale with which China is expanding its nuclear and conventional arsenals", as he said the world was entering a "dangerous new age of proliferation".
"During the Cold War, we benefited from a series of negotiations and dialogues that improved our understanding of Soviet doctrine and capabilities, and vice versa," Sir Stephen said in a speech in Washington.
"This gave us both a higher level of confidence that we would not miscalculate our way into nuclear war.
"Today, we do not have the same foundations with others who may threaten us in the future — particularly with China."
Ms Truss would launch a “New Commonwealth Deal” aimed at strengthening economic relations with member countries.
Ms Truss's plan would hasten bilateral trade deals with Commonwealth partners.
Her campaign team claims it would greatly strengthen the Commonwealth trade cost advantage, which is already 21 per cent lower on average for trade with those countries compared with non-members.
“I will ensure the Commonwealth sits at the heart of my plans for Global Britain," Ms Truss said.
“As one of the largest groups of freedom-loving democracies, we must ensure there are clear benefits to remaining a member of the Commonwealth and offer nations a clear alternative to growing malign influence from Beijing.
“Prioritising trade with countries across the Commonwealth will strengthen economic and security ties whilst also turbocharging opportunities for British businesses to access one of the world’s largest economic blocs.”
A campaign representative said: “Liz believes the Commonwealth is vital to countering the influence of China and other authoritarian regimes seeking to undermine democratic values and freedom.
“She believes trade and investment has a key role to play in stopping the growing Chinese influence, where Beijing has used investment as a part of its ‘Belt and Road Initiative’.
“As prime minister, she will maximise all opportunities to strengthen economic and security ties across the Commonwealth.”
But Liberal Democrat foreign affairs spokeswoman Layla Moran said Ms Truss was merely “reheating old promises while ignoring the huge damage her government has done to Britain’s reputation abroad".
“As Foreign Secretary, Truss has helped to oversee savage aid cuts to our Commonwealth allies, pushing desperate people into poverty," Ms Moran said.
“It shows all the rhetoric about Global Britain is just empty words.”