Budget airline EasyJet has branded a possible takeover approach from a US firm as "highly opportunistic".

The investment fund Castlelake revealed late on Friday that it was in the early stages of considering an offer for the Luton-based airline, but had not yet approached the firm's board.

Castlelake owns a stake of about 2.14% in EasyJet through the funds it manages, and valued the airline at a minimum of £3.06bn ($3.89bn).

The carrier said the takeover interest had come at a time when its share price had been pushed lower by worries over the impact of the Iran war on the airline sector.

EasyJet said on Monday: "The board notes the highly opportunistic timing when EasyJet's share price is temporarily depressed due to the current situation in the Middle East and its impact on customer confidence and jet fuel prices."

The American firm said any offer would be for "no less than" 403.23p a share.

Shares closed on Friday at 398p each, before the announcement was made, and surged by up to 12% in opening trade on Monday.

However, stock was down by more than 30% in the past year before news of the potential bid.

EasyJet highlighted its strong financial position and said it remained focused on its medium-term target to deliver more than £1bn ($1.27bn) in pre-tax profits.

The airline said it had also noted "the considerable regulatory, financial and other execution challenges associated with a potential takeover of EasyJet".

But it said it had a duty to maximise shareholder value and would "consider any proposal, should one be made".

Castlelake has until 17:00 BST on 26 June to make a firm offer or walk away under UK takeover rules.

Castlelake has assets under management worth £27bn ($36bn).

It entered talks in January with bankrupt US carrier Spirit Airlines over a possible takeover.

Castlelake has also previously bailed out collapsed Scandinavian Airlines (SAS) and then sold on its shares to Air France-KLM.

In interim results last month, EasyJet reported that bookings for summer flights had been lower than the same point last year because of uncertainty caused by the conflict in the Middle East.

It posted a half-year pre-tax loss of £552m ($700m), compared with a loss of £401m ($510m) a year ago.

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