Reuters could not determine if there were any conditions attached to the approval, which came less than three weeks after announcing the acquisition, reflecting the urgency of the transaction.

In the UK, regulators usually take up to 60 working days to approve the change. Representatives for UBS and Credit Suisse declined to comment.

On March 19, shortly after announcing the transaction, the Bank of England did not comment further, saying it welcomed the “comprehensive range of measures taken today by the Swiss authorities to support financial stability”.

UBS needs 58 countries to agree to the merger, which would make it Switzerland’s largest bank and asset manager with more than $3 trillion in assets. The longer it takes to close the deal, the more difficult it may be for Credit Suisse to maintain its business.

The United Kingdom, where Credit Suisse holds $60 billion in risk-weighted assets primarily in its investment banking division, is one of its largest markets outside of Switzerland.

UBS received a provisional green light from European Union antitrust regulators on Tuesday to acquire Credit Suisse, but still needs approval under EU merger rules, the European Commission said.

Ralph Hamers, chief executive of UBS, who will step down on Wednesday after the annual shareholder meeting, told reporters on March 29 that “plans can only be implemented partially” because Credit Suisse is still a separate entity.

“That’s why it’s so important to get the support of regulators globally and as soon as possible,” he said.

John Glenn, chief secretary to the UK Treasury, said last week that he had no immediate concerns about UBS’s implementation of the bailout of Swiss Credit Suisse.