"The invitation was extended at the G20" meeting in Hangzhou in September, when May met Chinese President Xi Jinping, a spokesman said.
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Chinese state councillor Yang Jiechi visited London in December for talks with Foreign Secretary Boris Johnson, where they discussed working together on global challenges such as North Korea and Syria.
Johnson also expressed the hope of closer trade ties as Britain eyes its future outside the EU - an issue that has seen May meet several world leaders in recent months, most recently US President Donald Trump.
Ties with China were strained last summer when May, shortly after taking office following the EU referendum, ordered a review of a £18-billion ($22-billion, 21-billion-euro) deal to build a Chinese-backed nuclear power point in England.
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She subsequently approved the project to build Hinkley Point, Britain's first nuclear plant in a generation, but not before Chinese state media accused the country of suffering from "China-phobia".
"I am committed to intensifying our trade relationship, including more market access for UK service exports and more Chinese investment in the UK," Johnson said after his meeting in December.
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