Global banks face an arduous and costly process if they decide to close businesses in Russia, banking sources and experts say, complicating decisions over whether they should withdraw.

Sanctions placed on Russia following its week-old invasion of Ukraine and retaliation from Moscow have raised questions over how much longer banks can continue.

One banking source raised particular concerns about how banks navigate an order on rouble lending and the implications for foreign companies in Russia. Banks are also weighing the risk to their reputations in staying there.

While banks have not yet announced exits, at least one global lender with operations in Russia is creating an in-house team and working with outside lawyers and consultants to determine whether and how it could exit before making public announcements, one banking source said.

“For an oil company, walking away from refinery assets in Russia might be as simple as dropping the keys and leaving but a unilateral exit is not possible for a financial services firm,” said Dan Awrey, a professor at Cornell Law School.

Under normal circumstances, banks would not be able to exit a country without the consent of its regulators and central bank. They would also need a willing buyer to take control of their loans and other commitments, experts say.