But remains 'confident' server problems won't affect UK release.
EA has apologised to users who were left unable to play SimCity after the publisher's online service Origin was crippled by "overwhelming demand".
Some fans attempting to play the city-building game, which launched in North America yesterday, reportedly faced lengthy delays while attempting to connect to EA's Origin servers, which the game requires in order to function.
EA later acknowledged the issue, confirming that it was "experiencing overwhelming demand which is keeping some users from accessing their games", and issued an apology.
"The SimCity servers are currently inundated with the masses of eager mayors attempting to govern their cities," the publisher said on its website.
"Some players may currently be experiencing issues or delays when attempting to join a game server or region - or may be unable to create a city at this time. Additionally, there are intermittent reports of friends list, invite, and tutorial delays and errors. We are working to clear traffic from the roads and hope to have all players managing their cities as soon as possible.
"We're sorry for any inconvenience this may cause and appreciate your patience while we work on a resolution to this issue."
EA has previously faced criticism for its approach to SimCity's DRM, which requires an always-on internet connection to function.
However, the publisher says that it is "confident" that server issues won't plague the game's international release later this week.
"We're making changes to prevent further issues," the publisher said in a follow-up tweet, "and are confident that Origin will be stable for international launches later this week."
SimCity launches in the UK this Friday, March 8.
Source: Twitter, EA.com