WASHINGTON (Reuters) - U.S. Republican Senator Bob Corker said on Monday that he could oppose his party’s tax bill over deficit concerns in an expected Senate Budget Committee vote this week, but added that Republicans were working to resolve his concerns. “I’m not threatening anything. I’m just saying it’s very important for me to know that we’ve got this resolved,” Corker told reporters. Asked if he could vote ‘no’ on the tax bill at a committee hearing slated for Tuesday, he replied: “Very possible. Yeah. Sure.” Corker is among a group of deficit hawks who want the tax  legislation to contain a backstop measure that would raise revenues in the event that expected economic growth does not materialize to compensate for nearly $1.5 trillion in deficit spending over the next decade.        