The leaders of all five Central American countries as well as the Dominican Republic will crowd into the White House on Thursday in a show of strength intended to kick-start the ailing efforts by the administration of President George W. Bush to push a controversial trade agreement through Congress.

With the administration still far short of the votes needed for passage of the Central American free trade agreement (Cafta), the presidents have spent this week in a highly unusual nation-wide effort to lobby recalcitrant lawmakers.