Latest: Portsmouth face delay to secure Brighton loanee ahead of rivals Sheffield Wednesday - but deal is secure

The highly-regarded 19-year-old has agreed a loan switch and passed a medical ahead of becoming the Blues’ 13th recruit of the transfer window.

However, Brighton are unwilling to sign off the move until after Tuesday’s cup clash with Crawley.

The Republic of Ireland Under-21 international is pencilled in for involvement in the second-round clash against the League One side.

As a consequence, the Seagulls are reluctant to let O’Mahony depart until such playing commitments have been met - either as squad involvement or back-up.

It means it could be Wednesday before the teenage striker is able to link-up with Pompey, albeit still comfortably before Friday’s deadline day.

That would allow him to be considered for a Blues debut in Saturday’s visit of Sunderland to Fratton Park.

O’Mahony started Brighton’s final match of last season’s Premier League campaign, lining up against Bournemouth in April.

He was withdrawn at half-time of the 3-0 defeat, yet totalled three top-flight outings and four Bristol Street Motors Trophy appearances in a breakthrough season.

However, with Brighton currently splashing out and strengthening their squad, boss Fabian Hurzeler is keen to let the youngster leave on loan to maintain his promising development.

Sheffield Wednesday have also shown interest in the former Cork youngster, but Fratton Park has been pinpointed as the preferred destination.

O’Mahony will bolster a frontline missing last season’s top scorer Colby Bishop, having undergone heart surgery earlier this month.

Although Kusini Yengi is now back after recovering from a groin issue, appearing as a second-half substitute in Saturday’s 2-2 draw at Middlesbrough.

Meanwhile, Christian Saydee, who has been operating as a centre-forward during Pompey’s striker shortage, netted twice in a man-of-the-match display at the Riverside Stadium.

Mousinho’s striking options are also to be boosted by O’Mahony, who joined Brighton’s Academy in January 2023 for an undisclosed fee.