President Obama on Sunday delivered his first remarks about Mitt Romney’s new running mate, Rep. Paul RyanPaul Davis RyanRepublicans are avoiding gun talks as election looms The Hill's 12:30 Report Flake to try to force vote on DACA stopgap plan MORE (R-Wis.), welcoming the vice presidential pick to the race and issuing a critique of his policies.

“Just yesterday, my opponent chose his running mate, the ideological leader of Republicans in Congress, Mr. Paul Ryan,” said Obama at a fundraiser in Chicago, according to a White House pool report. “I want to congratulate Mr. Ryan. I know him, I welcome him to the race.”

But the president made clear he would draw a sharp contrast between his policies and those of the Romney-Ryan ticket.

“He is a decent man, he is a family man, he is an articulate spokesman for Governor Romney's vision but it is a vision that I fundamentally disagree with," said Obama.

Obama criticized the GOP for promoting what he called a “top down” economic system and said those policies were “central to Gov. Romney and ... central to his running mate.”

Romney campaign spokesman Ryan Williams criticized the comments in a statement, accusing Obama of running “a fear and smear campaign because his policies have failed.”

“President Obama’s campaign has accused Mitt Romney of committing crimes and killing people, and now they are attacking Paul Ryan. They have lost all credibility,” he added.

Democrats have moved quickly since Romney tapped Ryan to be his running mate on Saturday to paint the seven-term lawmaker as outside the mainstream, with senior campaign advisers David Axelrod and Stephanie Cutter blasting the House Budget Committee Chairman’s plans.

The Obama campaign has focused its attacks on the Ryan budget which would cut $5 trillion, overhaul the tax code and shift Medicare to a subsidized private insurance model.

Axelrod on Sunday likened the Medicare reform plan to a “Trojan horse” that would kill the program.

He said Ryan’s selection was a “pick that is meant to thrill the most strident voices in the Republican Party, but it's one that should trouble everybody else, the middle-class, seniors, students.”

Vice President Joe BidenJoseph (Joe) Robinette BidenDems ponder gender politics of 2020 nominee Trump: Why didn't Obama 'do something about Russian meddling?' 2020 Dem contenders travel to key primary states MORE delivered a friendlier welcome to Ryan, calling him on Saturday to congratulate him on being Romney’s running mate. Biden "urged Congressman Ryan to enjoy the day with his family, and said he looked forward to engaging him on the clear choice voters face this November," according to a statement from the Obama campaign.

Biden though has also been a tough critic of Ryan in the past saying in June that he was a “fine guy” but adding “I think his ideas are not nearly as fine as he is a man.”

Obama arrived in Chicago on Saturday and is scheduled to attend a series of fundraises in his hometown, including an event in the backyard of his home to mark his 51st birthday, which he celebrated last week.

On Saturday, Obama held a meeting with political staff at his campaign headquarters in Chicago, a spokesperson told reporters.

— Updated at 5:46 p.m. to include a response from the Romney campaign.