America Online has allegedly stepped up its attacks against the Microsoft messaging service, kicking users of Microsoft's program off AOL's system entirely. Microsoft and AOL have been fighting for weeks over instant messaging. Microsoft wants to be able to connect users of its MSN Messenger to users of AOL's rival Instant Messenger, which AOL vehemently opposes, in part because the MSN program runs on AOL's servers. AOL has repeatedly attempted to block Microsoft from doing so. The latest flap involves a feature of AOL's Instant Messaging system. The AOL system lets users send "warnings" to other users when they do something inappropriate. Users who receive enough warnings are temporarily suspended from using the AOL Instant Messenger client. Microsoft officials said today that officials said today that AOL is exploiting that feature to knock MSN users off AOL. Users of the MSN Messenger program must also be logged on to AOL's Instant Messenger service if they want to talk to AIM users. According to Microsoft, AOL sent 'warnings' to AIM users who were logged in through MSN Messenger, and had them suspended from using the MSN client on the AOL system. "We're disappointed that AOL continues to confuse people with these types of messages and even worse, to disconnect them from using AIM," said Deanna Sanford, lead product manager at Microsoft. AOL bristled at this. "This is another Microsoft sideshow," said Andrew Weinstein, an AOL spokesman. "They are continuing to hack our system. And by doing so, they are confusing our users and creating these issues." Microsoft said it put up a patch last night to block AOL's move. If AOL is behind the warnings, the company runs the risk of alienating its users, said Lucas Graves, analyst at Jupiter Communications in New York. "It definitely begins to border on the area of inconveniencing the users for the sake of prosecuting this industry battle. And in general, in the long run, that's a place where AOL doesn't want to tread," he said. While the fight between the two companies escalates, others in the messaging industry are attempting to make peace. The Internet Engineering Task Force is currently working on a protocol for instant messaging that would allow systems using it to interoperate. And IP telephony company Pulver.com has decided to host a closed-door meeting for instant messaging companies in Melville, New York next month. Company officials said that around 20 companies had agreed to attend, although they would not say whether AOL or Microsoft would be there. Michael Fitzgerald contributed to this story.