Prague, Czech Republic - Bill Clinton defended the decision to expand NATO eastwards 25 years ago when he was president, at a conference in Prague on Tuesday marking the anniversary of the accession of the Czech Republic, Poland, and Hungary to the Western defence alliance.

"Sometimes you just have to take a chance and that’s what everybody involved 25 years ago decided to do," Clinton said.

"I think that it’s been a good investment."

"We did the right thing to expand NATO, and it keeps expanding," he added.

Donald Trump Trump threatens Republican congressman with a primary challenge for refusing to raise debt ceiling

The three former members of the Warsaw Pact, the alliance dominated by the Soviet Union, joined the alliance on March 12, 1999. The Warsaw Pact was dissolved in mid-1991.

Clinton thanked Czech President Petr Pavel for his initiative in finding 800,000 artillery shells for Ukraine from outside the European Union. He said the West had to stand by Ukraine for as long as it was fighting Russia.

But he also expressed the hope that there would be other options at some point.

"He probably won’t like my saying this, but President Putin is not gonna live forever any more than I am," Clinton said.

Addressing criticism that NATO expansion had ignored Russian security interests, Clinton stressed that he had attempted during his two periods in office ending in early 2001 to draw the Russians in, for example through the NATO-Russia Council.

"We offered them the chance to participate," he said.

Pavel presented Clinton with the Czech Republic's Order of Tomáš Garrigue Masaryk. Czech and German aircraft conducted a flypast over Prague to mark the celebrations.