"I was comfortable but I was uncomfortable," the highly-regarded ACT Brumbies coach said of turning down a chance to join the Wallabies to stay in Canberra.

The lure of coaching on the international stage is undeniable if not irrepressible, but McKellar suggests the timing isn't quite right amid a period of change in clubland.

McKellar knocked back an approach from Wallabies coach Dave Rennie to join the national set-up late last year, instead opting to "do what was right" by the club that took a chance on him.

The 44-year-old signed a one-year contract extension which sees him through to the end of 2022, giving him more time to achieve his goal of establishing the Brumbies program as a world leader.

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McKellar knew he would stay the moment Peter Hewat took an opportunity in Japan. In the latter's place came Rod Seib, who will remain a Brumby alongside McKellar and Laurie Fisher until the end of next year.

"I was comfortable because I knew I had to do what was right by the Brumbies, but uncomfortable because I felt like I was letting some people down, Dave Rennie in particular," McKellar said.

"I had certainly committed and was keen to help out and be involved, but the Brumbies are the club that gave me an opportunity for me to do a job for them.

"I just felt that with a couple of changes in staff, we couldn't put at risk all the good work we had done over the past couple of years. I wasn't prepared to take that risk, but at the same time I was really disappointed I'd potentially let Dave down.

"He's a good man and we've had some good conversations since, there are certainly no grudges held. He understood and was pretty good about it to be honest."

A one-year extension leaves the door open for McKellar to join the Wallabies ahead of the 2023 World Cup in France.

The desire to coach on the international stage burns brightly, but more pressing for McKellar is a chance to chase successive Australian championships.

"We'll see where it all gets to. One day I'd like to be involved at international level and we'll see where we get to," McKellar said.

"What's important now is doing my job, to make sure I put together the staff and players as best as possible to go to Perth on the 19th and get a result.

"Our goal is to be a team and a club considered to be in the best bracket in the world. For that to happen, we need to have the attitude of wanting to get better and better, daily.

"That's our bigger picture goal. Our short-term goal is to review a trial game and get our preparation right to beat the Force.

"I know it's a cliché and that sort of thing, but it really is day by day. If you get that right, we know with this group if we get our preparation right, then we generally can back that with good outcomes."