LOS ANGELES United Parcel Service (UPS) and the Teamsters union representing 340,000 employees at the package delivery firm plan to meet on Tuesday in an effort to avert a threatened strike on Aug. 1.

The scheduled meeting, which both sides have confirmed, would be the first since UPS labor contract negotiators deadlocked on July 5.

While the company and the International Brotherhood of Teamsters have reached agreement on multiple issues including air conditioning on delivery vans, the union is still pushing for better wages for part-time employees who account for about half of UPS workers.

Pressure is mounting on the parties. Teamsters-represented workers have vowed to strike if they do not have a deal when the current contract expires at midnight on July 31.

Investors have joined UPS customers in urging the two sides to avoid a work stoppage that would disrupt shipments across the country and create supply-chain backups that stoke inflation.

One estimate put the potential economic impact of a 10-day UPS strike at more than $7 billion, the costliest in modern times. That estimate from Michigan-based Anderson Economic Group includes UPS customer losses of $4.6 billion, lost wages of $1.1 billion and company losses of $816 million.

"The vast, vast, vast majority of shareholders are eager to see a strike averted," New York City Comptroller Brad Lander told Reuters.

Lander serves as investment advisor for the New York Retirement Systems, which held UPS shares valued at $191.1 million as of June 30.

He said the better option is for the company to put "a good deal on the table addressing the issue that the Teamsters have made quite clear is the remaining sticking point."

(Reporting by Lisa Baertlein in Los Angeles; Editing by Jamie Freed)