Democrats Jesse Jackson and Michael Dukakis squared off Tuesday in the West Virginia and Nebraska primaries as an impassioned Jackson insisted it's not too late for a comeback. Dukakis, meanwhile, called on Republican rival George Bush to detail his knowledge of drug allegations against Panamanian strongman Manuel Antonio Noriega.

Dukakis' comments came as aides to Bush fielded mounting questions about when the vice president first became aware of the allegations against the Panamanian strongman, who was indicted on federal drug charges in February. Bush did not campaign Monday and had no campaign appearances scheduled Tuesday.Jackson staged a primary-eve scramble for votes in Nebraska and West Virginia, while Dukakis, who has taken the last few days off from campaigning, spent the day at the Statehouse in Boston.

"This is a live race. . . . Every voter counts," Jackson declared Monday as he campaigned in Omaha, Neb. In Martinsburg, W.Va., he told supporters: "I'm coming to the last lap. I'm running longer and running stronger because my mind is made up. . . . Press on! Press on!"

Dukakis campaigned in the two states last week.

Tuesday's contests do not offer an especially large share of Democratic delegates - 37 in West Virginia and 25 in Nebraska. Of the 2,081 delegates needed to nominate, Dukakis has 1,519.7 to Jackson's 933.1 according to the Associated Press' count.

But two more victories would help cement Dukakis' grip on the nomination, which aides have been saying he could clinch in the season-closing primaries June 7 in California and New Jersey.

For Jackson - who won last week's District of Columbia primary but notched no primary victories in the six weeks prior to that - a strong showing in either state would be a welcome respite.

Even before Tuesday's contests were decided, Jackson was heading for the next battleground: Oregon, which holds its primary a week from Tuesday, with 45 Democratic delegates at stake.

Dukakis met Monday with New Jersey Sen. Bill Bradley, and aides said the two talked about U.S.-Soviet relations. Bush has already made Dukakis' lack of foreign policy experience an issue.

Bradley said he did not think Dukakis was vulnerable on the issue.