Three days after Merck & Co. Inc. lost a huge liability case last month over the pain-reliever Vioxx, chief executive officer Richard T. Clark told his 64,000 employees to stand fast.

“We have great strengths as a company, a business that is fundamentally sound, and a critically important life-saving mission,” Clark said in a memo to employees after jurors ordered Merck to pay a widow $253.5 million.

“Nothing in last week’s verdict changes that,” said Clark’s memo.

This week, Clark’s confidence and his employees’ faith will be tested in their own backyard. The nation’s second Vioxx trial will begin in Atlantic City, pitting a heart-damaged Vietnam War veteran against the New Jersey-based pharmaceutical company.

Both sides have a lot at stake. A second defeat for Merck would further sock morale and increase pressure to consider settlements to mitigate damages.

A Merck victory could boost morale and deflate pressure for a settlement.

This week’s case is being brought by Frederick Michael Humeston, 60, of Boise, Idaho, who was on Vioxx four years ago when he suffered a heart attack.