ZURICH (Reuters) - A Swiss far-right campaign to curb immigration from the European Union, potentially unraveling bilateral ties with the bloc, moved ahead on Tuesday when the government gave proponents a green light to start canvassing public support.

Should the initiative win the required 100,000 signatures by July 2019, it would go to a vote under the Swiss system of direct democracy. That could pave the way to scrapping the free movement of EU citizens now guaranteed under bilateral accords.

The populist Swiss People’s Party (SVP) has long sought to limit immigration to neutral, landlocked Switzerland, whose population of 8.4 million is already one-quarter foreign.

The European Union insists that its citizens must be able to live and work in non-member Switzerland as the price for enhanced Swiss access to the EU single market, the biggest for Swiss exports.

The latest campaign comes at a sensitive time for bilateral ties, which soured last month when Bern promised to retaliate over what it called unacceptable limitations on the access of Swiss stock exchanges to the EU single market.

Voters approved quotas on immigration in 2014 but parliament instead opted in 2016 for a system giving people registered as unemployed in Switzerland first crack at open jobs. This move skirted a clash with Brussels and averted a threat to bilateral relations.

The text of the new initiative states that Switzerland will unilaterally steer immigration and enter no accords granting foreigners free access. It would give the government 12 months to negotiate an end to the current free movement pact, one of more than 100 bilateral accords that regulate ties.

Should negotiations fail, the government has 30 days to cancel the free movement accord. This would almost certainly prompt Brussels to cancel an entire package of other bilateral agreements that stand or fall together.

A survey of more than 20,000 people by newspaper publisher Tamedia this week, however, found 55 percent opposed cancelling the free movement deal and 42 percent in favor.