Senate Minority Leader Mitch McConnell (R-KY) says that the U.S. tax system is unfair to the wealthiest Americans.

"I understand full well that our friends on the other side live to every day to raise taxes," McConnell told CBS host Charlie Rose on Tuesday. "Almost 70 percent of the federal revenue is provided by the top 10 percent of taxpayers now. Between 45 and 50 percent of Americans pay no income tax at all."

"We have an extraordinarily progressive tax code already," he added. "It is a mess and it needs to be revisited again."

According to the Congressional Research Service (PDF), almost 100,000 millionaires in the U.S. pay a lower effective tax rate than millions of families earning less than $100,000.

Earlier this year, Republicans in the Senate blocked the Paying a Fair Share Act, which would have enacted a rule named for billionaire Warren Buffett, who revealed that he paid a lower tax rate than his “secretary.” An April CNN poll found that 72 percent of Americans — including 70 percent of independents — favored the “Buffett Rule.”

The Kentucky Republican also told Rose that he was prepared to work with President Barack Obama and House Speaker John Boehner (R-OH) towards a "grand bargain" to lower the nation's debt.

"The challenge we have, Charlie, for the future is the unsustainable path of our entitlements, very popular programs," McConnell insisted. "The eligibility for which needs to be adjusted in order to meet the demographics of America. Regretfully after six months of discussions the Speaker and I had with the president, the president was unwilling to make those kind of eligibility changes unless we gave him such a huge tax increase that it would have brought the economy to a halt."

"We are prepared to do a grand bargain," he continued. "You have to have a willing president. You don't get these deals done without a president who is serious about getting an outcome."

"Many people who know wrote about that and suggested that in the end when push came to shove, it was the Speaker that was not prepared for the grand bargain," Rose pointed out.

"I read the same articles," McConnell replied. "I thought we came out very well on the Republican side in Congress."

Watch this video from CBS's This Morning, broadcast June 19, 2012.