Timeline - ACS's Hochtief sparks takeover battle for Abertis

(Reuters) - German builder Hochtief (HOTG.DE), controlled by Spain's ACS (ACS.MC), made a 17.1 billion euro (£15.2 billion) bid for Spanish toll road operator Abertis (ABE.MC) on Wednesday, topping a rival offer from Italy's Atlantia (ATL.MI).

Hochtief is offering 18.76 euros in cash, or 0.1281 Hochtief shares, for each Abertis share and has set a minimum acceptance threshold of 50 percent plus one share.

The move creates a dilemma for Abertis, which has also received a cash and shares offer from Atlantia worth around 15.7 billion euros on a comparable basis, according to analysts.

Below are some of the key events related to the battle for Abertis, in chronological order:

** April 21 - Italian toll-road operator Atlantia says it's interested in buying Abertis, but only if a deal can be agreed.

** April 26 – Abertis says it has not received a concrete bid from Atlantia.

** April 27 - Atlantia agrees to sell 10 percent of its domestic motorway unit to a series of investors for 1.48 billion euros as it presses ahead with plans to bid for Abertis.

** May 2 - Sources say Atlantia and Abertis will meet in Italy to discuss plans for a tie up.

** May 4 - Atlantia denies a press report from Spanish newspaper Expansion saying an offer on Abertis is "imminent". The Rome-based group confirms that talks with Abertis are ongoing.

** May 10 - Sources say that banks BNP Paribas, Credit Suisse, UniCredit and Intesa Sanpaolo are putting together a bridge loan of around 11 billion euros for Atlantia's potential takeover bid for Abertis.

** May 15 - Atlantia launches a cash-and-share offer for Abertis, valuing the Spanish rival at 16.34 billion euros.

** June 15 - Atlantia's offer is registered. It says it intends to keep Abertis on the stock exchange with at least a 5 percent free float.

** July 3 – Spanish market regulator CNMV admits the application to proceedings.

** July 5 - Spanish newspaper El Economista reports that JP Morgan is looking at a possible offer for Abertis with Globalvia, citing unidentified financial sources.

** July 19 – Spanish airports operator Aena (AENA.MC) says it was prevented by its state shareholder Enaire from making a bid for Abertis.

** July 21 - Spanish builder ACS (ACS.MC) confirms media reports it is studying a counter-bid for Abertis.

** July 26 - Abertis posts a 17 percent rise in first-half core profit.

** Aug. 2 - The chief executive of Atlantia does not rule out sweetening the terms of an offer for Abertis.

** Aug. 16 – According to Spanish newspaper El Confidencial, infrastructure funds invited by ACS to take part in a bid for Abertis raise doubts about the structure of the transaction.

** Aug. 29 - ACS is sounding out Chinese funds with headquarters in Hong Kong to partner on a potential counter-bid for Abertis, Expansion newspaper reports.

** Aug. 30 - El Confidencial reports ACS's bid could be made through Hochtief (HOTG.DE), its German unit.

** Sept. 29 - Atlantia says Banco Santander is acting, together with Credit Suisse and Mediobanca, as financial adviser to the company on its takeover bid for Abertis.

** Oct. 9 - Spain's regulator CNMV authorizes Atlantia's bid for Abertis

** Oct. 10 - Abertis says CNMV sets the acceptance period for Atlantia's bid as Oct. 10 to Oct. 24

** Oct. 13 - EU regulators approve Atlantia/Abertis tie-up

** Oct. 18 - ACS's Hochtief announces bid for Abertis

(Compiled by Joanna Jonczyk-Gwizdala and Nadiia Karpina in Gdynia; Editing by Mark Potter)