Ukraine-focused Cadogan now has until 5.00pm on April 21 to announce a firm intention to make an offer for Ascent, which has interests in Slovenia, or walk away.
Shares in Ascent rose sharply on Thursday, before the Easter break, obliging Ascent to issue a statement revealing the approach.
Cadogan's house broker Cantor Fitzgerald said the two companies share complementary acreage.
Ascent’s Slovenian operations are in close proximity to existing processing facilities, intra-field and national pipelines, while Cadogan’s Ukraine E&P business remains steady.
Production from Debeslavetska and Cheremkivska (gas) and Monastyretska (oil) licences in Western Ukraine is currently around 122 barrels per day net.
Cantor has a price target of 36p and 'buy' rating on Cadogan, where the shares rose 11% to 10.85p, while Ascent leapt 69% to 3.30p.
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