The Magpies boss was talking after a pre-season friendly at the newly-named SportsDirect.com Park, where a well-taken goal for new signing Siem de Jong was overhauled by strikes from Latics substitutes Timothee Dieng and William Gros.
Netherlands international right-back Janmaat underwent a medical on Tyneside on Tuesday.
Meanwhile, French striker Emmanuel Riviere, also 24, is on the verge of a £5million switch from Monaco.
When asked about the Janmaat deal, Pardew told Sky Sports: "That's pretty close, but that's about as good as I can say really at the moment.
"I've obviously been involved in the game today so I don't know really the detail of it, but we're being active at the moment and we need to be, because we need to be stronger than we were last year, for sure."
Newcastle's proposed unveiling of Janmaat, which was initially expected on Tuesday afternoon, is now unlikely to take place on Wednesday either, although the delay is purely administrative.
Janmaat has been signed to replace France international Mathieu Debuchy, whose proposed move to Arsenal has been on hold while the Magpies have tied up the Dutchman.
On Riviere, Pardew added: "That's another one that we're talking to... it's difficult to say that they're not done, but he's obviously a player that we have some interest in."
De Jong gave Newcastle a 14th-minute lead at Oldham, powering home a fierce effort after his initial free-kick had rebounded off the wall.
But after a flurry of changes, Dieng headed a David Mellor corner past Jak Alnwick to equalise on 69 minutes and then trialist striker Gros, formerly of Kilmarnock, muscled his way through to score the winner eight minutes later.
Newcastle now head out for their pre-season tour of Australia and New Zealand, with their next friendly fixture against Sydney FC next Tuesday.