KIEV, Ukraine (AP) — Russia is building up its land forces and weapons along the border, Ukraine's president said Saturday as German Chancellor Angela Merkel warned Russia not to block Ukrainian ports in the Sea of Azov.

Tensions between Russia and Ukraine were still escalating a week after a naval clash in the Black Sea on Nov. 25 in which Russia fired on three Ukrainian naval ships then seized them and their 24 crew members.

Across the world in Argentina, foreign leaders grilled Russian President Vladimir Putin about Russia's actions, but he remained firm, squarely blaming Ukraine for the co...