The airport where world leaders are expected to land this weekend for the state funeral of the Polish president was closed today by the volcanic ash cloud.

But the Polish government said it had no immediate plans to delay the event.

A spokeswoman for Krakow Balice Airport said it was closed to all traffic "indefinitely" because of the spreading volcanic ash cloud emanating from Iceland.

Despite the closure, she said, "preparations to receive" world leaders on Sunday were continuing, as the government said it had no firm plans, yet, to postpone the state funeral of President Lech Kaczynski in Krakow.

"A two-day perspective ahead of the arrival of those planes is a relatively long time and it is hard to say how the situation will influence the arrivals," she said. "All we can do is wait."

A Presidential Palace spokesman said there had been no discussion so far of postponing the funeral, but "theoretically, there exists such an option." Any delay would be an "absolute last resort."

Among world leaders who said they would come to the funeral are President Barack Obama, Russian President Dmitry Medvedv and German Chancellor Angela Merkel.

Late last night the White House said Mr Obama still planned to fly to Poland on Saturday.

A spokesman said, "It's something that we're keeping an eye on. Right now, our schedule is still on."

Poland is preparing a tradition-laden funeral for Mr Kaczynski and his wife, who were among the 96 people killed when their plane crashed on approach to Smolensk. They were headed to the airport for a commemoration of the systematic execution of thousands of Second World War Polish army officers by Soviet secret police in 1940.

President Kaczynski's family wants the funeral to go ahead as planned.

The Presidential Palace spokesman said: "It is the will of the family that, under no circumstance, the date of the funeral be changed."