Ally McCoist, the manager at Ibrox, made public at the weekend his interest in landing the young Irishman, who is out of contract at Tannadice in the summer and has been linked with a host of top clubs including Italian side Palermo.
McNamara, who lost former United captain Jon Daly to the Glasgow side last summer, is preparing to face McCoist's men in a potentially volatile William Hill Scottish Cup semi-final at 'neutral' Ibrox next month.
"Rangers haven't been in contact with us and I wasn't aware that Ally had spoken about Gunning," he said. "I'd be surprised about it because I'd expect - if they've spoken to Gavin - that Rangers would have called us first to say so. Ally did that last year. He gave me the courtesy of call to say they were speaking to Jon Daly.
"So I'd be surprised if they'd spoken to Gavin. Listen, we're all looking at players. I watched the Barcelona-Real Madrid game on Sunday night - but I'd do well to get any of them. I don't know if it's mind games, you'd need to ask Ally.
"But in my mind the semi-final is weeks away - we have more important stuff to focus on. In the week leading up to the semi-final, we'll turn our attention to it."
United, who sit fourth in the table, take on Inverness Caledonian Thistle at home tomorrow night as they refuse to give up on their target of finishing second in the SPFL Premiership. "Results have been good," said McNamara. "That's seven out of eight we've won. It's a good time to be hitting a bit of form and hopefully we can keep it going until the end of the season. All we can do is to try and keep winning.
"To be fair to Aberdeen and Motherwell, they keep winning as well, which makes it that bit more difficult for us.
"You want to be in good form at this time of the season, especially if you're still in cup competitions.
"If we can keep that going in the next few weeks, including the semi-final, it will give us a good chance of reaching the final."