Bill Gross of Janus Capital Group Inc said on Tuesday that German 10-year Bunds were "the short of a lifetime" and that the trade could earn 10-15 percent over a period of one to two years.

"It's certainly a trade that doesn't cost you anything in the short-term because it doesn't yield anything, and it has an ultimate potential of 10 or 15 percent over a one- or two-year period," the closely watched U.S. bond investor told cable television network CNBC.

Gross had previously said in a tweet on Tuesday that German 10-year Bunds were "the short of a lifetime. Better than the pound in 1993. Only question is Timing / ECB QE." 

Gross, who told CNBC his Janus Global Unconstrained Bond Fund was "in the trade" as of the last reporting period at the end of March, also said the risk was "minimal" relative to the reward and suggested the trade could earn more through leverage.

"You've got 200 basis points of spread to narrow between German bunds and U.S. Treasuries," Gross said. "If levered, gosh, maybe you don't do as well as Soros and Druckenmiller, but it comes close," he said.

Gross was referring to investors George Soros and Stanley Druckenmiller, who made their names betting against the pound in 1992.

German 10-year Bund yields have hit fresh record lows since the European Central Bank began purchases of public-sector bonds on March 9 as part of its trillion-euro stimulus program, with the latest low of 0.049 percent touched on April 17.

The benchmark 10-year U.S. Treasury yield, by comparison, was last at 1.92 percent.

The ECB has committed to buying 60 billion euros of assets a month with newly created money until September 2016, or longer if needed, to get inflation back on track to hit its target of just below 2 percent.

Gross also opined on the U.S. Justice Department's announcement Tuesday of the arrest of a high-frequency trader in Britain over charges he manipulated the futures market and played a role in sparking the 2010 "flash crash."

Gross said he would point not to one individual, but to leveraged financial market conditions.

"These things happen, it's really a function of leverage and the ability I suppose of one individual or one firm to impose their will on the market for a short period of time," Gross said.