Janet Yellen has canceled a planned trip to Portugal this week amid international market instability resulting from the Brexit vote, a Federal Reserve official confirmed Monday morning.

Yellen, the central bank's chairwoman, was supposed to take part in a panel Wednesday with Bank of England governor Mark Carney at a forum hosted by the European Central Bank.

Instead, she will return to Washington following a meeting of the Bank of International Settlements in Basel, Switzerland, that took place this weekend. The Bank of International Settlements is an institution created for coordination between central banks.

Yellen and other Fed officials have been concerned about the effects of the United Kingdom's vote to leave the European Union, which has roiled foreign exchange, bond and stock markets.

The Fed released a statement Friday in the immediate aftermath of the vote that it was "carefully monitoring" developments and prepared to act if necessary.

A surging dollar and falling financial markets, even if they don't generate a financial panic, will change the course of the Fed's monetary policy over the medium term. Although the Treasury, under U.S. law, is reponsible for value of the dollar, a significantly stronger dollar is among the factors that might lead the Fed to delay tightening monetary policy, as it would slow exports and put downward pressure on inflation through lower import prices.