Barack Obama defended one of the men vetting his running-mate prospects Tuesday after the adviser came under fire for receiving favorable loan terms from a sub-prime lending company Obama has criticized.

The Illinois senator kept the adviser -- former Fannie Mae CEO Jim Johnson -- at an arm's length, but heartily rejected the suggestion that he should do background checks for unpaid members of a search committee, no matter how influential their task may be.

"I mean this is a game that can be played -- everybody, you know, who is anybody who is tangentially related to our campaign I think is going to have a whole host of relationships," he said in St. Louis, Mo. "I would have to hire the vetter to vet the vetters. I mean at some point, you know, we just asked people to do their assignments."

Although presumptive Republican nominee John McCain has sought to use the connection to his advantage this week, Obama downplayed his connection with the team, which includes Caroline Kennedy and Eric Holder, a former deputy attorney general and U.S. attorney for the District of Columbia under President Clinton.

"These aren't folks who are working for me," Obama said. "They are not people, you know, who I have assigned to a job in the future administration, and ultimately my assumption is that this is a discrete task that they are going to be performing for me in the next two months."

The presumptive Democratic nominee was responding to criticism after The Wall Street Journal reported that Johnson, who is leading his three-member vice presidential search team, received more than $7 million in loans from Countrywide Financial Corp. The Journal reported Johnson received at least two loans at below-market rates as a result of a relationship he had with the company's CEO Angelo Mozilo.

In its reporting, The Wall Street Journal said it found nothing illegal about the loan terms, and an attorney for Johnson said the loans were in the bounds for those to people with credit backgrounds like Johnson's.

Obama has criticized Countrywide on the stump, and the McCain camp continued its attacks on Obama for the connection Tuesday.

"It's preposterous for Senator Obama to claim that the leader of his VP selection committee isn't working for him. Barack Obama has castigated Countrywide Financial, but now that Jim Johnson has been exposed for taking sweetheart deals from Countrywide's CEO -- Obama is in a state of denial," McCain spokesman Tucker Bounds said in a statement. "It's that brand of weak leadership and hypocrisy that shows why Barack Obama has no record of taking courageous stands or making change in Washington."

Obama said Tuesday, "I am not vetting my VP search committee for their mortgages."

He said Johnson and the other two members on the running-mate search team are "performing that job well," and stressed that their positions are volunteer and unpaid.

FOX News' Bonney Kapp contributed to this report.