Tarnawa is one of 14 entries to remain in the reckoning for Sunday's Qatar Prix de l'Arc de Triomphe after the initial forfeit stage, but her main market Adayar and the Aidan O'Brien-trained Snowfall are set to be added to the race at a cost of €120,000 on Wednesday morning.
Dermot Weld's mare won a Group Three on her return this season and Tarnawa then pushed St Mark's Basilica all the way in the Irish Champion Stakes over a mile and a quarter last time out.
Derby and King George hero Adayar is one of two planned contenders for Charlie Appleby and Godolphin, along with St Leger victor Hurricane Lane, who is already entered in the race.
O'Brien has last year's star filly Love and Group One winner Broome among the 14, with Oaks winner Snowfall another who set to be added to the contest.
She suffered a shock defeat at the hands of Roger Varian's Teona in the Prix Vermeille on her latest outing, and the pair could renew their Longchamp rivalry.
St Leger runner-up Mojo Star, who is handled by Richard Hannon, and the William Haggas-trained Alenquer complete a formidable Irish and British line-up at this stage.
Home hopes currently rest with outsiders Baby Rider, Sealiway and Bubble Gift – with Raabihah also in the mix, although she holds alternative entries in the Prix de Royallieu and Prix de l'Opera on Arc weekend.
Japan's pair of Chrono Genesis – the mount of Oisin Murphy – and Prix Foy winner Deep Bond add an extra international element, with German runner Torquator Tasso the other possible at this stage.
There is a second forfeit on Tuesday, before Wednesday's supplementary entries, with the final declarations on Thursday.