The union representing Canada's striking foreign service workers is asking Treasury Board President Tony Clement to settle the dispute through binding arbitration.

Tim Edwards, the president of the Professional Association of Foreign Service Officers, made the offer Thursday in a letter to Clement.

The letter, which sets a deadline for the offer of noon Tuesday, says the job action is having an impact on tourism, education, air transport and agriculture, and is also delaying the processing of visas and immigration applications.

"He will review it and act in due course," Clement's spokesman, Matthew Conway, said in an email. "Our government will always put the interests of taxpayers first. We will continue to bargain in good faith."

Clement has told the union he has made a fair and reasonable offer, and has urged its members to return to work. "If you sincerely believe that the government's offer is 'fair and reasonable,' you should not be concerned with presenting that position to an independent third party," Edwards writes.

"We sincerely believe that Canadian taxpayers and Canada's economy have suffered enough and it is time to bring closure to our dispute."

Job action started in April

Alternatively, Edwards said the union would be satisfied to return to the bargaining table if the government brought a new offer. Talks between the sides broke down in early June when Treasury Board returned to the table with no new offer.

The union's 1,350 members have been in a legal strike position since April, and have been staging rotating job action in Ottawa and at foreign missions.

The union wants wage parity with their counterparts in other federal departments that make as much as $14,000 more for doing similar work. Earlier this week, Edwards and Clement got into in a public argument over Twitter. The minister told The Canadian Press he wasn't going to "fold like a $3 suitcase" under the union's pressure.

Treasury Board has said it is negotiating in good faith towards a deal that is fair to taxpayers as well as employees. It says the foreign service jobs are well-paid and highly sought after.

"We're not asking them to fold. We're simply asking them to come to the table, engage with us meaningfully and to make a reasonable attempt at finding a compromise solution," Edwards told a press conference on Parliament Hill.

He said the government is being pressured by "some very significant players in the Canadian economy" to settle the dispute.

That includes Nova Scotia Premier Darrell Dexter, who plans to raise the issue with fellow premiers at a meeting in Ontario next week, said Edwards.

Impact on tourism

Conway said the government wasn't going to address the union's particular concerns in public "in order to respect the confidentiality and legal obligations of collective bargaining and to bargain in good faith."

Tourism groups have estimated that the strike could cost the industry $280 million this summer, while some foreign students have been forced to withdraw from Canadian university courses because they can't get visas in time.

The Canadian Alliance of Student Associations said earlier this week that international students are dependent on receiving their study permits. International students contributed $8 billion to the Canadian economy in 2010, the alliance said.

"We are worried that students waiting for permits will start their courses late or be denied admission altogether," Jonathan Champagne, the organization's national director, said in a statement.

Edwards said visa processing dropped 65 per cent in June at the three major processing centres in Beijing, Mexico City and New Delhi targeted by the strike.

He also said that more than a dozen trips by federal cabinet ministers have been cut short or cancelled because of the targeted withdrawal of services by its members abroad.