Workers at two stores in Omaha have sent letters to the company stating their intent to form a union, according to Starbucks Workers United, which shared the letters on its social media accounts earlier this month.

The letters, from workers at stores at 72nd and Dodge streets and 125th Street and West Center Road, cite issues with staffing, scheduling and training in their push for unionization.

Starbucks spokesperson Andrew Trull said in a statement that while the company believes a direct relationship with employees is best, “we recognize that a subset of partners feel differently — and we respect their right to organize and to engage in lawful union activities without fear of reprisal or retaliation.”

Trull said Starbucks welcomes the opportunity for partners “to vote in a neutral, secret ballot election conducted by the NLRB — which allows all partners to make their own informed decision regarding union representation.”

The two Omaha stores are among a growing number across the country that have sought to be unionized. So far, that number is approaching 400, which is about 4% of Starbucks stores nationwide. That includes the Lincoln Starbucks location at 27th Street and Kensington Drive, which became the only unionized company location in Nebraska earlier this year.

Unionized employees at more than 200 stores, including the Lincoln one, conducted a walkout on Red Cup Day in November, when the company hands out tens of thousands of free reusable cups, one of its busiest customer traffic days of the year.

None of the unionized locations have yet been able to negotiate a contract with Starbucks, and negotiations have been stalled for the past few months, although CNBC reported that Starbucks has proposed resuming talks in January.