The people insisted on anonymity because they were not authorized to discuss the negotiations publicly.
Union negotiators believe Miller favors employers in disputes, for example claims that workers are intentionally slowing down cargo movement. In a letter to members last week, the union's president wrote that negotiators for employers were unwilling to budge because their side benefits from the current system.
Miller told The Associated Press he is aware that he has become the focal point of the closed-door talks but is unsure why. He figures that in the hundreds of decisions he has issued, he upset someone who is now getting back at him.
"I'm bewildered as anybody else on the outside looking in," Miller said.
U.S. Labor Secretary Thomas Perez entered the standoff on Tuesday in San Francisco, where he settled into his new mission of forging a new contract. Perez does not have legal authority to force an agreement, but outsiders hope he can coax one that would end the protracted troubles.
Spokesmen for the International Longshore and Warehouse Union and the Pacific Maritime Association, which represents shipping lines that carry cargo and port terminal operators that handle it once ships dock, declined comment, citing a media blackout.
As negotiations drag on, the consequences of the cargo bottleneck are rippling through the U.S. economy.
The 29 ports on the West Coast handle about $1 trillion worth of goods annually, including Asian imports such as electronics, household goods and clothing as well as U.S. exports such as produce and meat.
Honda Motor Co. is slowing production at six factories in Ohio, Indiana and Canada due to parts shortages. California citrus exporters say exports are half of normal to places such as Korea, Japan and China. Examples from impacts on industries abound.
On Tuesday, 32 massive ocean-going vessels were anchored and awaiting a berth at the twin ports of Los Angeles and Long Beach — the nation's largest port complex. The scene was similar outside the smaller ports of Oakland, and Seattle and Tacoma in Washington state.
Lines grew notably longer over the holiday weekend, when employers again locked most longshoremen out of work rather than pay enhanced wages.
Employers say dockworkers are intentionally slowing down, an allegation the union denies. On Tuesday, employers hired full work crews for the first time since Friday.
Currently, Miller and three other arbitrators oversee separate areas of the West Coast and are effectively appointed for life. The union wants either side to be able to dismiss an arbitrator when a contract expires, with both sides agreeing on a replacement. Recent deals have lasted six years and the one being negotiated could last five.
The maritime association wants to keep the current system. It has argued that if arbitrators are subject to reappointment they might not rule independently due to worries they might offend one side and jeopardize their future.