As the venue wars between AEG and Azoff Music Group were heating up, AEG attempted to pressure superstar band U2 into signing a letter saying it would play the Staples Center in Los Angeles in order to secure a date at the O2 Arena in London for a yet-to-be-announced tour, Amplify has learned.

It’s unclear if U2, which is managed by Live Nation-owned Maverick, signed the letter, but many viewed the attempt as an overreach, adding momentum to an initiative by Live Nation’s UK Chairman Denis Desmond to file a complaint with England’s Competition and Markets Authority over the pairing of the O2 and Staples Center, which AEG acknowledged in a July 3 letter.

Now AEG finds itself in a tough position — continue a policy that has been successful in getting a few extra shows to play Staples Center, but has been roundly criticized by artists, managers and promoters as being heavy-handed; or end the policy amid pressure from regulators and abandon a strategy that had helped the company steer several A-list acts toward Staples Center.

Besides U2, AEG successfully pushed Shania Twain to play Staples Center in exchange for a concert at the 02. When the band 30 Seconds to Mars was routing their tour, AEG backed off the tying agreement between O2 and Staples Center — the band is managed by Azoff and it’s believed AEG wasn’t spoiling for that fight.

In total, AEG is believed to have convinced four or five bands to sign the tying agreement. Unlike AEG, which solidified its policy in writing, Azoff MSG Entertainment said it never had an official block booking agreement between the MSG and The Forum. In a letter to Billboard, Azoff said it took a nuanced approached to booking and said it had no official block-booking policy.

When Katy Perry’s Witness Tour was being routed, the Garden booked two dates for her in early October despite her decision to play three nights at the Staples Center in November. Sources say the move was an attempt to show AEG that Azoff MSG Entertainment wasn’t enforcing block booking, but by now, AEG’s block booking policy for the O2 and Staples Center were so successful the company didn’t want to let it go.

Yesterday, both sides seemed to reach a truce in the four-month-old fight, issuing lengthy statements for a Billboard story. AEG said it would drop its tying arrangement between Staples Center and the O2 if the Forum would end its tying arrangement with Madison Square Garden.

“AEG will consider reverting to its previous long-standing position that its buildings are open to all artists. The only thing that would make us happier than if Mr. Azoff officially declared that MSG will no longer prevent artists from choosing Staples Center would be if they then actually follow through with it,” a statement from AEG read.

That prompted Azoff to declare an end to the rivalry, telling Billboard “(we) are thrilled that AEG has listened to the artists and is going to adopt the same booking policy as MSG. For the record, and at the risk of being redundant: MSG and The Forum are open buildings. We said it and we mean it. Just ask the artists like Katy Perry who played MSG and Staples. So, that settles the matter: AEG and MSG have open buildings.”