Hearts have a 13-point advantage in third place in the Clydesdale Bank Premier League and lead fifth-placed United, who finished third last season, by 15 points having played just one game more.
Houston, who is a former youth-team coach at Hearts, said: "I have a lot of admiration for Hearts, certainly for the two guys running the team. I worked for them for years and I like them personally and professionally."
He added: "I said last year when they got the job they were the best two guys for the job.
"What they've done is even better than I thought they would do.
"The season they've had has been absolutely sensational.
"They've won loads of games and they are at least the third best team in the league this season, there's no question about that.
"We know we're going to be in a tough game."
Source: PA
Source: PA