WASHINGTON – Defense Secretary Rumsfeld, stung by criticism that he’s insensitive to the needs of the troops and their families, offered his most impassioned defense yesterday.

The normally stoic Mr. Rumsfeld said when he meets wounded soldiers or relatives of those killed in battle, “their grief is something I feel to my core.”

“I am truly saddened by the thought that anyone could have the impression that I, or others here, are doing anything other than working urgently to see that the lives of the fighting men and women are protected and are cared for in every way humanly possible,” he said. “And I hope and pray that every family member of those who have died so bravely knows how deeply I feel their loss.”

Mr. Rumsfeld has been a lightning rod since the war began in March 2003, but criticism recently intensified after a Tennessee National Guardsman in Kuwait asked him during a question-and-answer session with soldiers on December 8 why he and his comrades had to scrounge for armor to protect their vehicles.

Mr. Rumsfeld gave an extended answer that included the statement, “You go to war with the Army you have, not the Army you might want or wish to have.”

Critics called the response insensitive and castigated him for not doing more to prepare the American military for the Iraqi invasion and its aftermath.

The following week, some Republicans joined Democrats in voicing dissatisfaction with Mr. Rumsfeld.

Senator McCain, a Republican of Arizona, said he had “no confidence” in Mr. Rumsfeld, citing the defense secretary’s handling of the war and the failure to send more troops.

The defense secretary was criticized again last weekend when it was reported that he did not personally sign letters of condolence to the families of dead soldiers, but instead relied on a mechanical device to affix his signature. He immediately abandoned the practice.

President Bush defended Mr. Rumsfeld, who has agreed to stay on for Mr. Bush’s second term, saying his defense secretary was “doing a very fine job.”

Yesterday, Mr. Rumsfeld said, “I, and I know others, stay awake at night for concern for those at risk, with hope for their lives, for their success. And I want those who matter most, the men and women in uniform and their families, to know that.”

Asked whether the criticism had undermined his ability to do his job, he said, “You get up in the morning and you think about what our troops are doing. And I must say, if they can do what they’re doing, I can do what I’m doing.”