WASHINGTON (CNN) -- Sen. Barack Obama suggested Thursday that he doesn't see any point in having another debate with Democratic rival Sen. Hillary Clinton.

Wednesday's debate on ABC may be the final face-off between Sens. Hillary Clinton and Barack Obama.

Clinton has agreed to a debate next week, but Obama has not accepted the invitation.

At an appearance in Raleigh, North Carolina, Obama said he has a lot of campaigning to do in a limited amount of time.

Obama said he had agreed to an earlier debate, but Clinton declined that one.

"I'll be honest with you, we've now had 21," he said. "It's not as if we don't know how to do these things. I could deliver Sen. Clinton's lines; she could, I'm sure, deliver mine."

Obama said he has to look at his schedule, considering the upcoming primaries.

The two Democrats went head-to-head in a debate Wednesday night on ABC.

During the first part of that debate, the candidates largely rehashed the controversies that have marked their past six weeks on the campaign trail.

Much of the fire was leveled at Obama, who once again answered questions about controversial statements by his former pastor, the Rev. Jeremiah Wright, and his own comments that some rural Pennsylvanians are "bitter."

Obama said it took too long for them to address anything substantial.

"Last night, we set a new record, because it took us 45 minutes before we even started talking -- until we started talking about a single issue that matters to the American people," he said.

"Now, I don't blame Washington for this; that's just how Washington is. ... They like stirring up controversy; they like playing 'gotcha' games. ... I will say Sen. Clinton looked in her element." Watch Obama note how long it took to get to the debate issues »

Clinton hasn't commented on the debate.

Meanwhile, all three of the major White House hopefuls sat down for one-on-one meetings Thursday with British Prime Minister Gordon Brown as he visited Washington.

Brown, on his second trip to the United States since replacing Tony Blair last year, held private 45-minute sessions with each candidate at the British Embassy.

Clinton and the British leader discussed a wide range of issues, including the wars in Iraq and Afghanistan and global warming, according to Senate aides.

Obama said he and Brown talked about strengthening the U.S.-British alliance, and "common challenges" such as the Iraq and Afghanistan wars, instability in the global economy and support for democracy and prosperity in Africa.

"The prime minister has been a critically important partner for the United States, and I look forward to working with him in the months and years ahead to enhance the special relationship between the United States and the United Kingdom," Obama said in a statement.

It was Obama's first meeting with Brown. Watch the two have a sitdown at the British Embassy »

The British leader and Sen. John McCain, who met last month in London, were heard talking about the presidential election during a photo op.

McCain said the drawn-out process in U.S. campaigns sometimes made one wish for the much shorter duration of the British system.

Brown laughed, saying his system has its ups and downs, too.

After her stop in Washington, Clinton resumed her campaigning in Pennsylvania.

The senator from New York was scheduled to hold a town hall-style meeting in Haverford and attend a rally in Philadelphia. She was also expected to appear on Comedy Central's "The Colbert Report."

Meanwhile, Obama was looking ahead to the May 6 contest in North Carolina, where early voting began in some counties Thursday.

On Friday, the senator from Illinois will launch a four-day tour through Pennsylvania, leading up to the state's primary Tuesday.

Pennsylvania, with 158 delegates at stake, marks the first Democratic contest in six weeks.

Obama leads Clinton in the overall delegate count, 1,644 to 1,498. Clinton has a slight edge in superdelegates, with 248 backing her compared with 226 for Obama.

Clinton holds a lead of 5 percentage points in Pennsylvania, according to an average of four recent surveys: Zogby (April 15-16), Franklin & Marshall (April 8-13), Los Angeles Times/Bloomberg (April 10-14) and Quinnipiac (April 9-13).

Clinton held double-digit leads over Obama until the past two weeks

McCain, who became the presumptive GOP nominee last month, had no public events scheduled Thursday.

The senator from Arizona expanded on his economic proposals in an interview with CNN on Wednesday, a day after he unveiled his plan.

"Americans need some relief," McCain said of his proposal to suspend the federal tax on gasoline and diesel fuel temporarily. Watch what McCain says about the economy »

"I just think it's kind of a good thing to do so people can have a little more enjoyable summer during tough times," he added.

McCain, long an advocate of cutting federal spending, also explained his push for certain measures that probably would delay achieving a balanced budget if he wins the White House.

"The best way to have a balanced budget is to have a recovering economy," he said.

The 71-year-old senator also shot down remarks from Rep. John "Jack" Murtha, D-Pennsylvania, that he may be too old for the presidency.

"Speak for yourself, Jack. I'm doing fine, thanks," he said in response to Murtha, who's 75. E-mail to a friend

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