Mexico's new warmth toward Cuba seen as strategic posturing.(Originated from Knight-Ridder Newspapers)

MEXICO CITY _ President Ernesto Zedillo is stepping up ties with Cuba with a series of high-level diplomatic exchanges that is to be capped by a state visit to Mexico by Cuban President Fidel Castro.

In a highly publicized succession of visits that is puzzling foreign diplomats, more than half a dozen top Mexican officials _ including the ministers of foreign relations, education and environmental affairs _ have traveled to Havana in recent weeks.

Cuba's economic czar, Carlos Lage, has received a red-carpet welcome in this capital, and Castro has accepted an invitation to visit here at a soon-to-be-decided date, Mexican Foreign Minister Jose Angel Gurria has announced. Among other activities, Castro will accept an honorary doctorate from the Autonomous University of Puebla.

Some …