SCRANTON, Pa. (AP) _ Presidential contenders George W. Bush and Al Gore dug in deeper Wednesday in their dispute over when and where to debate. Bush unveiled a new ad saying Gore's stance proved him untrustworthy.

Bush said he would stick to the schedule he has proposed, while Gore said the candidates must first agree to three widely telecast debates sponsored by the bipartisan Commission on Presidential Debates.

``When it was politically convenient, Gore said he'd debate anytime, anyplace, anywhere,'' an announcer says in the new, 30-second spot. ``Now that Governor Bush has accepted, Gore says 'unacceptable.' ... If we can't trust Al Gore on debates, why should we trust him on anything?''

On NBC's ``Today,'' Bush said ``I'm showing up'' in Washington for the first debate in his plan _ to be shown only on NBC and moderated by ``Meet the Press'' host Tim Russert _ even if Gore doesn't. ``I hope he shows up,'' Bush said.

But an NBC spokeswoman said the network would not give Bush a solo prime-time platform. ``We offered a debate, not an appearance,'' said spokeswoman Barbara Levin.

Gore sounded unpersuaded by Bush's talk. ``I'm not going to play games to try to substitute a talk show for the national bipartisan commission debates,'' Gore said on ABC's ``Good Morning America.''

He said his campaign has agreed to meet with the Commission on Presidential Debates to try to work out a compromise. But Bush, asked whether he also is willing to have his staff negotiate with the commission, replied: ``These are the three debates I'll do.''

Gore has accepted the commission's proposal for three 90-minute debates that would be carried by all major television networks. Bush wants only one of those three, plus one each that would be broadcast only by NBC and CNN.

``What's wrong with those commission debates? Is it that too many people will be watching?'' Gore asked on CBS' ``Early Show.'' He added, ``I'm happy to do all of these other talk shows and debate formats but not as a substitute.''

Both candidates were talking pocketbook issues in battleground states Wednesday, with Gore delivering an economic address in Cleveland and Bush touting his $1.3 trillion plan for tax cuts and his $158 billion plan for covering prescription drugs under Medicare.

Also Wednesday, Bush was highlighting military readiness in a speech to the American Legion convention in Milwaukee. Gore declined an invitation to address the veterans' group. Bush also was appearing later in the week with retired Gens. Colin Powell and Norman Schwarzkopf.

Gore's campaign said the American Legion event conflicted with the vice president's speech on economics.

In addition to Bush promoting his 10-year tax plan at a rally, the Texas governor and one-time front-runner in the presidential race has taken out full-page ads in Wednesday editions of USA Today in select cities, boasting endorsements from 300 economists who support the proposal.

He was devoting Thursday to national defense, with Social Security as Friday's likely topic.

But it is health care that has been especially prickly for Bush. Gore long ago released his prescription drug plan and spent weeks daring Bush to lay his own on the table.

Gore also succeeded in forcing Bush off-message by ridiculing him for authorizing campaign ads that broadly promised health care reform before Bush's own plan was released.

After a weekend at home in Texas, Bush on Tuesday announced details of a Medicare drug plan that he said would offer senior citizens more choices and quicker coverage than Gore's program.

``Keeping the promise of Medicare and expanding it to include prescription drug coverage will be a priority of my administration,'' Bush pledged at a senior citizens' residence.

His plan would restructure Medicare by forcing the government program to compete with private plans for the first time. Bush said Gore's competing $253 billion, 10-year plan would provide ``resources without reform.''

Gore, in turn, contended the Bush plan would leave ``millions of seniors without any prescription drug coverage'' and that he won't have the money to pay for it if he spends as much of the expected federal surplus on the promised tax cut as he has proposed.

Bush's plan would give states $48 billion immediately to help low-income seniors pay for drugs while a longer, $110 billion overhaul is being phased in. Another $40 billion would be spent to increase reimbursements to Medicare providers.

Bush also was asked on NBC whether he regretted making an off-color remark about New York Times reporter Adam Clymer. ``I said what I said. I'm a plainspoken fellow,'' Bush said, adding he regretted that the comment was picked up by a microphone.