Investors should be wary heading into next week, as a confluence of factors is likely to make Monday's trading session a rough one, Art Cashin, director of floor operations for UBS Financial Services, told CNBC.
Cashin said the street is expecting the debt debate in Washington to reach a boiling point on Monday and traders are closely watching the runup to a potential government shutdown.
(Related: Senate set to OK budget bill but shutdown looms)
"The showdown on Monday is a problem for traders and portfolio managers—it's the end of the quarter," Cashin said on "Squawk on the Street" Friday. "There's a lot of things to be planned and done for the end of the quarter."
"You're going to watch the clock tick down to whether we have a shutdown or not. So, it's going to be a very tough Monday," he added.
However, he said that if the debate doesn't resolve itself on Monday, it will likely be because of Washington's quagmire, where each party will look to blame the other for a shutdown. Republicans "may try as a ploy is to offer temporary emergency funding, a resolution that covers three weeks or a month, and if the president turns that down, then he shuts the government down. … That would then meld into the debt ceiling [debate]."
(Related: Gartman: Even government can't ruin this rally, buy stocks)
As a result, "we are in the bizarre position where credit default swaps on U.S. Treasury securities is beginning to move up," Cashin added. "The world's favorite safe haven has suddenly got credit default swaps moving on it."
— By CNBC's Paul Toscano. Follow him on Twitter @ToscanoPaul and get the latest stories from "Squawk on the Street" Disclaimer