The logo of German chemicals maker Covestro is pictured outside its headquarters in Leverkusen, Germany, July 26, 2019.
The sign of change from Covestro's previous stance comes after two top-15 investors of the plastics and chemicals maker told Reuters last month that it should engage in formal takeover talks in the interest of its shareholders.
The German group's shares were up 8.6% at 51.96 euros at 1445 GMT, their highest level in about 18 months.
In August, ADNOC indicated to Covestro, which has not commented on the takeover approach, that it could raise its informal offer to 60 euros conditional on the German company entering formal talks, Reuters reported at the time.
That non-binding offer would value Covestro, a maker of chemicals used in insulation, upholstery foams, coatings and transparent engineering plastics, at about 11.6 billion euros ($12.4 billion).
Persons:
Wolfgang Rattay, Abu, ADNOC, Ludwig Burger, Urvi, Elisa Martinuzzi, Jason Neely
Organizations:
REUTERS, Abu Dhabi National Oil Company, Reuters, Covestro, BASF, Bloomberg News, Thomson
Locations:
Leverkusen, Germany, Abu Dhabi, Frankfurt, Bengaluru