PRAGUE (Reuters) - Czech President Milos Zeman launched his 2018 re-election bid on Friday, saying he had decided to run due to his strong public support and because he wanted to offer continuity.

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Zeman, who has pushed for better ties with Russia and China and backed Donald Trump in the U.S. presidential race, has been a polarising figure in Czech politics, drawing protests in large cities but rallies in smaller towns where he gets his support.

His first term has been marked by battles with a Social Democrat-led government, sniping at reporters, warnings about Muslim immigration to Europe and efforts to improve relations with powers to the east.

Speaking at a televised news conference, the 72-year-old vowed to stay out of debates or campaigning but showed he was unlikely to alter his public comments.

He said media attacks had pushed him to run. He also took a question in Russian, repeating his opposition to European Union sanctions against Moscow.

“I will not declare any new programme. My programme is the continuity of performing the presidential task the way it has been done so far,” Zeman said.

“I admit one of the significant factors in my decision to run was the Czech media. Each of their attacks encouraged me more to run. Thank you, Czech media,” he added.

Zeman had told about 1,000 of his supporters on Thursday that he would seek a second term - news that quickly leaked - before making his decision public on Friday.

A former Social Democrat prime minister, Zeman has been in politics since Soviet-backed communist rule ended in 1989. He won a direct presidential vote in 2013 and remains one of the country’s most popular politicians.

His only challenger so far is businessman and writer Michal Horacek, who has launched a campaign with the motto “We can do better”.

While governments run domestic and foreign policy, the president can hold influence over the EU country’s often shaky multi-party cabinets. Zeman has differed with the current administration over his opposition to EU sanctions imposed on Russia for the annexation of Crimea in 2014.

At Friday’s news conference he answered a question from a Russian journalist asking about criticism of him for being too close to Moscow by joking - in Russian - that he was seen as an “agent” for many states by his critics. He then reiterated that sanctions should end.

Zeman has helped steer his country towards China and aims to visit both Russia and China this year. He will meet Trump at the White House in April.

Before his term ends, he will also name the next prime minister after an October parliamentary election in which no party is likely to gain a majority. Analysts say he could tie this to support for him.