SINGAPORE/NEW YORK: Greece's huge global diaspora is dishing out advice to friends and relatives on how to vote in Sunday's referendum and some feel so strongly they are buying expensive tickets to get home to cast their own ballots.

One airline put on extra flights and ticket prices have risen for expatriates who want to have a say in whether Greece accepts a cash-for-reform deal from international creditors or rejects it, potentially leading to a euro zone exit.

Konstantinos Dimitriou, a management consultant who lives in Singapore, is catching a plane early on Saturday and making the 19-hour journey back to Athens to vote 'Yes' to accept a deal.

"All the opportunities I got in my life to grow came in part from Greece's relationship with Europe, not just my Greek passport," he said.

He said the best man from his wedding was also flying back from New York to vote, as were two friends from Dublin and a former business partner from Sweden.

New Jersey-born John Sitilides, an international relations specialist who consults with the U.S. Department of State on Greece-related issues, said many Greeks and Greek-Americans in the United States were lobbying voters.

"They're emailing, their Facebooking, they're tweeting and they're phone calling," he said

The push was mostly to vote 'Yes', Sitilides said, a result that supporters see as keeping Greece in the euro zone and which probably would lead to the fall of leftist Prime Minister Alex Tsipras' government.

Dimitriou also said nearly everyone he knew who was flying back to vote will be voting 'Yes'.

The hefty costs of travelling to Greece from America - a last-minute round-trip ticket from New York to Athens runs about $1,400 and as much as $5,000 to other areas - may deter some.

The surprise announcement about the referendum, made just a week ago, also came at short notice.

"I wish I could (go), and I would vote 'Yes'," said Chicago resident Renee Pappas.

BRINGING SUPPLIES

Endy Zemenides, executive director of the Hellenic American Leadership Council, said many Greek-Americans travel to their native country in the summer months anyway, and those there who are qualified will be hoping to vote.

They have also been drawn into the crisis in other ways.

"I know people who are stocking up on staples, like medications, to take to older relatives," Zemenides said.

Aegean Airlines is putting on extra flights to and from Brussels and London Stansted.

It said it was offering return seats in economy class for 199 euros($221.13) to and from Brussels and for 148 pounds ($231.32) to and from London without a suitcase.

But deals are not to be found everywhere.

"The tickets to go to Greece this weekend are really expensive," said Dimitri Augustidis, who runs a tourism website in Britain and is heading back himself.

"It isn't because of the season, it's because of the elections. For the (general) elections in January, I went back to vote and paid 100 pound)to go two days beforehand. This referendum when I'm leaving again two days before, the tickets are 300 pounds." ($1 = 0.6398 pounds) ($1 = 0.8999 euros)