According to the rules he has set himself, Mr Bushby cannot use any form of mechanised transport – including ferries.
Speaking from the roadside, he said: “It would be pretty miserable if it was a no.
“Even the Russians let me through [their country], despite world tensions.”
His support team told the BBC they had made repeated attempts to contact Channel Tunnel officials in order to seek permission but had yet to receive a response.
Mr Bushby, who wants access to a service tunnel separate to that used by the trains, said: “If I have to swim across, I obviously will. But it will be colder than the Caspian.”
Last year, he completed a 186-mile (300km) swim across the Caspian Sea – the first person to do so.
Mr Bushby plans to make a special delivery when he reaches Austria next year..
He said: “Back in Chile, right at the start of the walk, a doctor gave me 50 bucks and asked me to hand deliver a postcard to his brother in Vienna, Austria. I intend to do that. I expected it will be the longest-ever delivery time for any letter!”
