Referring to the concerns about the UK's economic relations with China she said: "Our national security always come first."
Last week's announcement by China to tighten export controls on rare earths and other materials that are key for advanced tech manufacturing led US President Donald Trump to threaten an additional 100% tariff on imports from China, raising the prospect of an all-out trade war between the two economic giants.
US Treasury Secretary Scott Bessent called China's move "economic coercion" and "a global supply chain power grab".
Asked about accepting the US offer to join it in its battle with China, Reeves said she was "very concerned" by China's actions and urged the Chinese government "not to put up barriers and restrict access".
She said the move was "bad for the global economy and creates further headwinds".
"I believe there are areas where we must challenge China, but there are also important opportunities to sell into Chinese markets, including financial services and other areas of the economy. We've got to get that balance right."
The chancellor also confirmed she was working with G7 counterparts "on our own critical minerals strategy, so that we are less reliant".