Aon has dropped any near-term plans to make an offer for rival Willis Towers Watson, while leaving the door open for a future move.

The company last week said it was in the early stages of considering an “all share business combination” with Willis Towers Watson, but back-flipped only a day later and declared it didn’t intend to pursue a deal.

Aon said the initial announcement was promoted by Irish regulatory disclosure requirements which were triggered by media speculation of a tie-up between the companies.

“Those regulations required Aon to make the disclosure at a very early stage in the consideration of a potential all-share business combination,” it said.

The regulations mean Aon’s announcement rejecting a deal now restricts it from making an offer for 12 months, subject to certain exemptions, such as a rival bid emerging or other material changes.

“Aon reserves the right within the next 12 months to set aside this announcement where so permitted,” it said.

The company’s New York-listed shares closed up 4.3% after it said it was not going ahead with a transaction. The stock rebounded from the previous day’s 7.8% slump that followed news of a possible deal.

Aon’s preliminary look at Willis Towers Watson follows Marsh & McLennan’s decision last year to acquire JLT in a $US5.6 billion ($7.9 billion) deal.