In a joint statement they said that this second leg match was an opportunity for both sides "to show the world how two cities with strong football legacies can show pride and leadership in the modern game".
The statement comes after tensions erupted into altercations during the first leg of the competition at Anfield - resulting in nine arrests.
Police Forces from both cities are working together, with the clubs, to provide "a robust approach to football violence".
Read the statement in full:
On Wednesday May the 2nd, two incredible teams will play the second leg of the UEFA Champions League Semi Final – Two world-quality and internationally renowned teams with rich, vibrant histories of playing in Europe.
For AS Roma and Liverpool FC fans, whether in Rome, inside or outside the Stadio Olimpico, or in the UK, those 90 minutes will be exciting, tense and some of the most thrilling moments of the competition so far.
They will join millions of football fans around the world who will enjoy the last game of the Semi-finals because it will provide the best football that the modern game can provide.
For that evening, Rome will be watched by the world and for millions of fans the game will represent passion, loyalty, rivalry and respect.
When AS Roma fans arrived in Liverpool, they were greeted with open arms, a warm welcome and an invitation to enjoy the city and the people who live here. Liverpool fans will receive the same warm welcome when they arrive at the footsteps of Rome, a city renowned for its beauty, passion and energy.
As Mayors of our two cities, we send the very best wishes to the teams, congratulate them on their achievements and encourage fans to enjoy the game, and the city of Rome. Fans should enjoy the rivalry on the pitch and respect outside the game.
Police Forces from both cities are already working together, with the clubs, to provide a robust approach to football violence. They will provide the safest possible environment and we hope that fans from both sides will respect the people of Rome, assist the authorities and agree that the best result on Wednesday is a vibrant, passionate, celebration of our teams and a safe, violence-free evening.
We both believe passionately in our cities. We believe we represent two peoples of incredible energy and joy and loyalty. But our cities also have compassion and kindness in common. Wednesday is an opportunity to show the world how two cities with strong football legacies can show pride and leadership in the modern game.