P&O Cruises is to amend Baltic cruises itineraries following the Russian invasion of Ukraine.
Norwegian Cruise Line and Viking Cruises have already dropped planned calls to St Petersburg.
Royal Caribbean International is reviewing plans for stops in the Russian Baltic Sea city as it continues to monitor the situation.
A P&O Cruises spokesperson said: “In light of the current situation with Russia and Ukraine we will be amending itineraries on Baltic cruises.
“Our top priority is compliance, environmental protection and the health, safety and well-being of our guests, crew members, shoreside employees and the people in the places we touch and we will advise guests of the changes as soon as possible.”
Sister brand Cunard echoed the P&O Cruises statement.
A Royal Caribbean spokesperson said: “The safety of our guests and crew is always our top priority. We are continuously monitoring events taking place around the world, including the situation in Ukraine.
“With the recent events, it is increasingly uncertain if we can visit St Petersburg, Russia, as scheduled. We have planned for alternative ports and will continue to monitor the situation over the coming weeks.
“Our guests and travel advisors will be the first to learn of any updates we need to make to keep everyone safe. Guests can feel comfortable knowing they are able to reschedule their cruise with our ‘cruise with confidence’ programme.”