Rep. Mike Castle (R-Del.) said Thursday that he’s leaning more toward running for Senate rather than another term in the House, if he decides to run for Congress again in 2010.

In an interview on Capitol Hill, Castle also acknowledged that several GOP Senators, including John McCain (Ariz.), have been pushing him in recent weeks to make the move to the other side of Capitol Hill. He said a final decision on his 2010 plans would likely have to come by early summer “at the latest.—

Castle’s comments come a week after former Delaware Lt. Gov. John Carney (D) filed to run for the First State’s lone House seat next year.

Castle said that he met last month with Carney, whom he considers a friend, and knew at that point that the former lieutenant governor was planning on jumping into the House race.

At that meeting Castle told Carney “there’s probably a better chance I’ll run for the Senate than the House. [But] I said there’s a chance I won’t run at all.—

While Castle believes he can beat Carney — a recent poll showed Castle winning a head-to-head contest — the Delaware Congressman said the race would represent his toughest challenge since his first election in 1992 against another former lieutenant governor, S.B. Woo (D).

If Castle does decide to run for Senate, it would likely set up a high-profile battle against state Attorney General Beau Biden (D), who is widely expected to run for his father’s old Senate seat next year. Sen. Ted Kaufman (D) was appointed to fill Vice President Joseph Biden’s seat after the 2008 election, but Kaufman has said he won’t run for the remainder of Biden’s term in the 2010. Castle will be 71 in 2010.

Between the Biden dynasty in the state and the expected involvement of the White House, a contest with Castle vs. Beau Biden would no doubt be one of the most closely watched battles of the 2010 cycle.

For that reason, people like McCain have been trying to convince Castle, who is a former Delaware governor, that he could do even more for the state in the Senate.

When they sat down for a half-hour meeting three weeks ago, Castle said McCain told him that “in the Senate, there’s the ability to do more … You’re one of 100 Senators. You could take on virtually any issue and make it yours.—