China significantly broadened its rare earths export controls on Thursday, adding five new elements and imposing additional scrutiny on semiconductor users as Beijing tightens oversight of the sector ahead of discussions between Presidents Donald Trump and Xi Jinping.

The world’s largest rare earths producer also added dozens of refining technologies to its control list and introduced rules requiring foreign rare earth producers using Chinese materials to comply with its regulations.

The Ministry of Commerce’s announcements follow a call from U.S. lawmakers on Tuesday for broader restrictions on the export of chipmaking equipment to China.

These measures expand the controls Beijing first announced in April, which had previously triggered global shortagesbefore subsequent deals with Europe and the U.S. helped ease supply pressures.

“The White House and relevant agencies are closely assessing any impact from the new rules, which were announced without any notice and imposed in an apparent effort to exert control over the entire world’s technology supply chains,” a White House official told Reuters on Thursday.