KIEV, Ukraine (AP) — A 90-day political campaign period has opened in Ukraine, where the incumbent president's future is uncertain.

President Petro Poroshenko hasn't yet announced whether he plans to run in a March 31 election, although he is expected to seek re-election. Monday marked the official start of campaigning.

A poll of 2,017 eligible voters published last week put Poroshenko's approval rating at just over 14 percent. Another likely candidate, former Prime Minister Yulia Tymoshenko, had support from 16 percent of those surveyed.

Other presidential hopefuls trailed behind the two. The Razumkov Center poll had a margin of error of 2.3 percentage points.

Ukraine has been hit hard by the tug-of-war with Russia, which annexed Ukraine's Crimea and backed a separatist insurgency in the country's industrial heartland in the east.