Democrats and Republicans need to support solid policies regardless of which party takes the lead such as President Donald Trump's decision to move the U.S. Embassy to Jerusalem and to pull out of the Iran nuclear deal, Joe Lieberman told CNBC on Thursday.
"Politics have become what they weren't when I became involved, which is the parties used to bring together people with different opinions and help to work with people from the other party to actually get things done," said Lieberman, who as Al Gore's running mate in 2000 became the first Jewish candidate on a major-party presidential ticket.
Lieberman, who said he's still a registered Democrat, is also friends with ailing GOP Sen. John McCain. McCain, a frequent Trump critic, wrote in his new book that he regrets not picking Lieberman as his running mate in 2008, when he ran for president against Democrat Barack Obama.
Democrats and Republicans are like "warring tribes," Lieberman said. "A lot of media coverage contributes to this tribal division in our country. And now it's beginning to seep down beneath the politicians," fermenting deep ideological polarization, he added.
He said the Trump administration "has done well" concerning the risks that Iran poses to the U.S. and the world. Exiting the nuclear deal negotiated by the Obama administration and threatening to reimpose sanctions are prudent steps, he said.
"This was always a bad deal," Lieberman said of Iran's 2015 agreement with the United States, the U.K., France, Germany, China and Russia to curb its nuclear program in exchange for lifting economic sanctions. "A nuclearized, radical Iran is the greatest threat to us, to world stability."
'"I worked a long time with a lot of other members of both parties in Congress to put those economic sanctions on Iran. They were intended to pressure Iran to give up its nuclear weapons program and to stop supporting terrorism and aggression in the Middle East," Lieberman recalled. "We gave up all that pressure on Iran for pretty much a pause in their nuclear program, and what turned out to be an acceleration of their other bad behavior."
Trump is "not leading from behind," said Lieberman, a criticism levied against Obama when he was in the White House. Lieberman is currently chairman of the United Against Nuclear Iran advocacy group.
"We're still the strongest economy in the world. And whatever the political elites in Europe, for instance, are trying to do now to save the Iran nuclear deal, their businesses are speaking," Lieberman said. He was referring to signals from European companies including, Total, Maersk and Allianz that they could exit Iran, fearing they could be hit by U.S. penalties for doing business there.
Negotiating from economic strength has also been an effective strategy for the White House concerning trade with China, Lieberman said. "The president does have leverage for China to renegotiate some of our trade agreements."
But the former senator cautioned Trump not to overplay his hand. "Please don't let it go to a trade war because that could really hurt our economy [and] could hurt the global economy."
WATCH: Lieberman cautions Trump against engaging in a trade war with China