OTTAWA -- As Prime Minister Stephen Harper prepares to celebrate the end of Canada's free-trade negotiations with Europe on Friday, there is persistent concern that two unhappy eastern European countries could still derail the deal.

Canada requires a visa for travellers from Romania and Bulgaria and some European diplomats worry that one or both of the countries could block ratification of the agreement if the requirement is not lifted, The Canadian Press has learned.

Harper is to host European Commission President Jose Manuel Barroso and European Council President Herman Van Rompuy for a Canada-EU summit Friday in Ottawa.

The event is being touted as a victory lap in what has been a protracted five years of negotiation of the wide-ranging trade and investment pact with Europe, known as CETA.

But one western diplomat, close to the talks, says the Romanian and Bulgarian visa issue remains an irritant.

"There is still a problem with the Romanians and Bulgarians. Canada requires a visa for them, which upsets them a lot," said the diplomat, who agreed to discuss the matter on the condition they not be identified.

"Yes, they're worrying that it could be a problem in their parliaments," the diplomat added. "It's still not totally clear if it will need to be ratified in national parliaments or only in the European Parliament."

Canada imposed the visa on the two countries as well as the Czech Republic to stop an influx of bogus refugee claimants among ethnic Roma applicants.

The Czech visa requirement ended last year, but Immigration Minister Chris Alexander said at the time the Romanian and Bulgarian ones would remain because of continued concerns over human smuggling and organized criminal gangs.

Alexander's office offered no new information on the Romanian and Bulgarian visas when contacted Thursday.

The potential problems in the parliaments in Romania and Bulgaria aren't the only ones bedevilling CETA. Earlier this summer, reports emerged that there was great dissatisfaction in Germany over an investor state dispute-settlement mechanism, known as ISDS.

An analysis of a leaked CETA text by the Canadian Centre for Policy Alternatives criticized the inclusion of ISDS, saying similar protections in the North American Free Trade Agreement have cost Canada $170 million in damages.

The analysis said Canada could face "billions of dollars in current ISDS claims related to resource management, energy and pharmaceutical patents." It also said the ISDS clause could "threaten existing and future environmental regulations."

Danish Trade Minister Mogens Jensen said in a recent interview that the ISDS provision has been improved from the previously leaked version that raised concern in Germany.

He said it now contains a "more precise definition à where you respect the right of every member state to regulate on labour standards, on environmental standards. That is basically what has been criticized."

Trade Minister Ed Fast said Thursday he's not worried about Germany blocking the deal over ISDS.

"We have no indication from the German government that in fact, they will not be supporting this agreement," he told reporters in Ottawa.

"We've also made it clear that from the Canadian perspective, we strongly support investor state dispute settlement rules, that protect investors as they do business within European Union and of course, that reciprocal and will protect European investors as they invest in Canada."

John Manley, head of the influential Canadian Council of Chief Executives, dismissed Thursday's report by the policy alternatives centre. "I never considered them a credible source of analysis."

As for the visa question, Manley said Romania and Bulgaria likely would not block ratification of CETA if "other practical work-arounds" can be found.

More needs to be done at European airports to block bogus refugee claimants from actually boarding flights for Canada. This could including closer tracking of travel documents used to board airliners, Manley said in an interview.

"We can't lift the visa until we find other ways to avoid this influx of refugee claimants."

Harper will have a new ally in Brussels later this year when Barroso's term as European Commission president comes to an end.

Former Polish prime minister Donald Tusk, with whom Harper has forged a strong relationship, assumes the presidency in December.

"He will definitely be the voice for openness, for growth and for a European economy that is open to the world and is more competitive. And CETA will bring exactly that," said Marcin Bosacki, Poland's ambassador to Canada,

"This process is complicated, but I don't foresee any substantial obstacles for ratification on the European side. And I do hope this is the same on the Canadian side."

Bosacki and Denmark's Jensen both predicted in separate interviews that it could take as long as two years before CETA is fully implemented because the final legal text is required and the deal needs to be ratified on both sides of the Atlantic.

"It's taken five years. It's always difficult with these processes," said Jensen. "We see the negotiations closed now, with the legal scrubbing going on."