Sky sources understand a second offer of £225,000 – an improvement of £50,000 on the original bid – was rejected by Championship rivals Hibernian this week for the highly-rated midfielder.
Rangers travel to Easter Road in the first round of the Petrofac Training Cup on Saturday, a repeat of the fixture at the same stage of the competition last year which Rangers won 2-1 after extra time.
Warburton told Sky Sports News HQ: “He’s a talented player but there are many, many talented players around the country and we have been interested in a number of players, that’s a fact. That one’s been documented.
“My job right now is to focus on my squad of players here and he’s not my player. It’s very disrespectful to talk about another club’s player so I will not do that.
“We are looking at one or two more players. The squad did very well the other night (losing 1-0 to Burnley) but we need to keep adding quality as and when we can.
“As long as it adds value on and off the pitch then we will be ok. A club like Rangers must always be looking to add quality.”