1.  Neither Cuban nor American officials have estimates of American visitors, saying the number is difficult to gauge because of unauthorized travel.

2.  Bush twice has recommended tighter restrictions on Cuba, not loosening the embargo, including making unauthorized travel to the island by American citizens more difficult.

3.  It also warned foreign passengers with such unauthorized travel permits on their passports that they may face difficulties at Singapore immigration checkpoints.

4.  Officials said too many people living in the United States have been making unauthorized travel to Cuba, often going there via Mexico or other Caribbean countries.

5.  They said too many people living in the United States have been making unauthorized travel to Cuba, often going there via Mexico or other Caribbean countries.