James Calveley Evans, 33, from Maes Pennant, Mostyn, Flintshire, appeared at Mold Crown Court on Friday.
He also pleaded guilty to three charges of distributing child sex images and three charges of possessing child sex images.
He has been further remanded in custody pending a pre-sentence report and will be sentenced in September.
Evans, who has been suspended as a North Wales Police constable, thought he was corresponding with a child by email, but it was an undercover police officer.
He admitted to the court he had attempted to arrange or facilitate a child sex offence in February.
But he denied a second similar offence in March, which the prosecution had agreed to lie on file.
Evans was also found to be downloading and distributing child sex abuse images and was found to have 607 photographs and 16 video images.
Judge Rhys Rowlands told him custody was inevitable and that it would "simply be a matter of the length of the sentence".

Morton had the best chance of the game, Bobby Barr's shot going through the legs of Hibs goalkeeper Mark Oxley and rebounding off the post.
Hibs looked tired and struggled to create clear-cut chances.
The result is a huge blow to the Edinburgh side's hopes as they attempt to pip Falkirk to second place in the Championship.
Manager Alan Stubbs rested midfielder John McGinn, who had been struggling with a back problem.
But Stubbs had to introduce the player midway through the second half as the visitors searched in vain for victory.
The first chance arrived on the quarter-hour mark, and it came for Morton - Mark Russell's long-range effort comfortably saved by Oxley.
Immediately after that, Hibs should have taken the lead. Liam Henderson was played through one-on-one with Derek Gaston, but the on-loan Celtic midfielder dinked his effort over the keeper and the bar.
Just before half-time Morton had a great chance to take the lead after a cross from Barr found the head of Declan McManus, but he failed to get enough on it and the ball trickled wide.
Hibernian struggled to create chances with the strike force of Jason Cummings and Anthony Stokes failing to click.
In the second half Stokes did produce a moment of real quality from 20 yards, a looping shot which Gaston did well to palm over.
Cummings then fired into the top corner of the net after being played in by Lewis Stevenson, but the assistant referee had his flag up for offside.
Morton almost took the lead after a mistake from Niklas Gunnarson allowed in Barr. His shot went through Oxley and came back off the post before Hibs scrambled to safety.
Hibs needed to add energy to their play and Stubbs introduced McGinn to the fray. The Scotland cap almost made an immediate impact, his shot from the edge of the area flying just over the bar.
But Stubbs' men failed to make that vital breakthrough against a resolute Morton side that looked solid throughout.
A North Wales Police officer has admitted trying to arrange a child sex offence over the internet.
[NEXT_CONCEPT]
Hibernian were held to a draw by a Greenock Morton side that more than merited a point.