Adds shares in paragraph 5, analyst comments in 6-7 and further detail in 9

By Kumar Tanishk

May 18 (Reuters) - Australian logistics group Brambles BXB.AX slashed its forecast for annual profit growth on Monday due to repair-capacity constraints in the United States, sending its shares tumbling to their biggest daily fall in more than two decades.

Short‑term repair bottlenecks driven by factors including labour shortages and subcontractor turnover resurfaced in April across the U.S. Central and Northeast, and are expected to dent full-year 2026 earnings by about $60 million, Brambles said.

With high customer demand, the Sydney‑based company also plans to ramp up pallet relocations, expand repair capacity and buy new pallets. It plans to purchase about 2 million new pallets in the fourth quarter to ease the squeeze.

The group now expects underlying profit to rise just 3%-5% in fiscal 2026 on a constant-currency basis, sharply lower than the 8%–11% growth seen previously. In 2025, it logged a 10% rise in underlying and operating profit from continuing operations on a constant‑currency basis.

Shares of the group fell 20.2% to A$17.63 in their sharpest daily drop since late November 2002 and were among the worst performers on the benchmark stock index .AXJO, which ended down 1.5%.

"The constraint is less about a single fix and more about rebuilding capacity across a fragmented network, like restoring signal coverage in a patchy communications grid while the system is still live," said Marc Jocum, senior product and investment strategist at GlobalXETFs.

The strain has already surfaced in earnings through higher relocation, among others, while the precise capital expenditure needed to permanently stabilise the system remains unclear, with automation and redesign rolling out incrementally rather than through a single big bang investment, Jocum said.

Brambles said it remains confident that the challenges will be resolved by the end of the first half of 2027.

Separately, the firm unveiled a fresh $400  million on‑market share buyback programme. It is set to kick off after its current programme and run through the balance of fiscal year 2026 and all of 2027.