The group operates more than 70 hotels in the UK under brands including Renaissance and Courtyard.
V-P of international PR June Farrell said Citigate would work alongside Marriott's retained corporate agency, Ellis Associates.
'The UK is an important market for Marriott. It is a source of outbound travellers to our hotels in 65 countries around the world,' she added.
The Washington DC-based firm has more than 2,700 lodging properties worldwide and pulls in annual global revenues of more than $10bn (£5.8bn).
V-P of international PR June Farrell said Citigate would work alongside Marriott's retained corporate agency, Ellis Associates.
'The UK is an important market for Marriott. It is a source of outbound travellers to our hotels in 65 countries around the world,' she added.
The Washington DC-based firm has more than 2,700 lodging properties worldwide and pulls in annual global revenues of more than $10bn (£5.8bn).