Billionaire investor Jeffrey Gundlach commented on the 10-year Treasury yield's march to near 3 percent on Monday.

"I've been of the opinion that closing above 3 [percent] would lead to an acceleration to higher yields. And we have not closed above 3," Gundlach said.

"The other big level – I think it's even bigger – is 3.22 [percent] on the 30-year, which we did close at; that was the high close this year, and then we backed off pretty nicely. But now we're back up around 3.16, 3.17, we're getting close again."

The yield on the benchmark 10-year Treasury note came within striking distance of the key psychological level of 3 percent Monday morning, a level some worry could trigger a reaction across financial markets. Investors worry that rising borrowing costs without underlying growth could backfire on the economy.

The 10-year rate is also important given its role as a benchmark for mortgage rates and other financial instruments. It has jumped in April on signs of increasing inflation and as the Federal Reserve signaled more rate increases are to come this year.

"What's interesting is the most recent rate rise [in the 10-year yield] – off of 2.72 to 2.99 this morning – it's hard for people to come up for with why it's happening," he added. "The bond market is kind of chronically weak in recent days, and I'm reminded of the old adage that you need buying to move prices up, but prices can fall of their own weight."

"I think it has something to do with all of this bond supply and these deficits that I've been talking about now for about 18 months. It's now here in real time: we're borrowing like $100 billion a month."

His comments came in an interview with CNBC's Scott Wapner from the sidelines of the Sohn Conference in New York.