Some U.S. financial institutions could be locked out of the European market if Donald Trump's administration repeals global rules imposed in the wake of the financial crisis, a top EU official said on Friday.

Valdis Dombrovskis, vice president of the European Commission and the EU's financial services chief, said international rules agreed during the 2007-09 crisis must be upheld to avoid undermining financial stability. "International finance needs international regulatory cooperation. Without it, we run the risk of regulatory arbitrage and renewed instability," Dombrovskis said in a speech in London. U.S. President Donald Trump signed an executive order last week to review Dodd-Frank, a U.S. law that implements a welter of international rules agreed by the United States, the EU and other major economies during the global banking meltdown.

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"We are sensitive to talk of unpicking financial legislation which applies carefully negotiated international standards and rules," Dombrovskis said. "Lax regulation in one country can create conditions for inadequate regulation and contagion throughout the world." Dombrovskis said the EU will uphold the reforms it introduced to toughen bank capital rules - based on the globally agreed norms - and will be "ready to take the necessary measures to protect and strengthen these achievements". The EU has allowed clearing houses, insurers and other financial firms from the United States and other non-EU countries to operate in the bloc because it deemed their home rules to be "equivalent" or as strict as those in the EU.

'Reassess the situation'