SCRANTON, Pennsylvania (Reuters/Bloomberg) - US Vice President Joe Biden said on Monday that Republican presidential nominee Donald Trump's remark that President Barack Obama founded Islamic State in Iraq and Syria had increased threats to the physical safety of US troops in Iraq.

"Trump is already making our country less safe," Biden told a crowd at a joint Scranton, Pennsylvania, in his first joint campaign appearance with Democratic presidential nominee Hillary Clinton.

He vouched for her empathy for the working class but then shifted into a scathing attack on Trump's grasp of national security and his remarks about Russian President Vladimir Putin and allies. He zeroed in on Trump's statement last week that President Barack Obama founded Islamic State in Iraq and Syria (ISIS), which the Republican has said was meant to be sarcastic.

"Let me tell you why it's a dangerous statement. As he might say, the bad guys are listening," Biden said, citing a reference to it made by the leader of Hezbollah.

"If my son were still in Iraq, and I say to all those who are there, the threat to their life has gone up a couple clicks."

Biden spoke less than an hour before Trump was to deliver a speech on national security in Youngstown, Ohio, like Scranton a battleground for both candidates in the November election.

Clinton's remarks in Scranton, a city where both she and Biden claim roots, were intended to make the case to Rust Belt voters that she cares about their fate more than Trump does. She called the economic plan Trump outlined last week a boon for the wealthy and for corporations.

Biden reinforced her remarks, saying she "understands the hope and aspirations" of working-class Americans, a category of voters Clinton has had trouble connecting with.

"She gets it," Biden said. "It's more than about her."