Switzerland's biggest bank, UBS, is reported to be in advanced talks to buy all or part of its troubled rival, Credit Suisse.
Credit Suisse's shares have fallen sharply in recent days after it said it had found weakness in its financial reporting.
There are concerns that Credit Suisse shares could fall 24% on Wednesday.
There has been no official statement on the progress of the negotiations, as the Swiss government held an emergency meeting on Saturday night.
UBS has asked the Swiss government to cover $6 billion 4.9 billion in costs if it were to buy Credit Suisse, according to sources quoted by Reuters.
The problems have coincident with the failure of two banks in the US - Silicon Valley Bank and Signature Bank - raising fears over the health of the banking system.