BEIJING - The man was in his 80s and dying. The woman was 73 and held his hand. They each lost a son in the 1989 Tiananmen Square crackdown and fought for decades to get China to acknowledge the deaths.

But Duan Hongbing wouldn't live to see that day.

"I held his hand and told him that I won't give up," the woman, Zhang Xianling, said she told Duan on a visit to his Beijing hospital bed. She said he squeezed her hand and closed his eyes in response, no longer able to speak. He died last year, a few days after that promise was made.

As the Tiananmen anniversary approaches Friday, aging parents of victims fear their cause will die with them. The oldest of the Tiananmen Mothers, as the group is called, is 94. The group's leader, retired professor Ding Zilin, says more and more members die each year.

"Can it be that you really want to wear us all down or wait for our deaths so that the problem will naturally disappear?" the group wrote in an essay addressed to the Chinese government and made public this week through the New York-based group Human Rights in China.

At the end, the 128 families who signed it attached the names of 22 former signers who have died.

China's government has never fully disclosed what happened when the military crushed the weeks-long, student-led protests on the night of June 3-4, 1989, possibly killing thousands of students, activists, and ordinary citizens.

Authorities try to stifle any public activities that remember those who died. That has long caused friction with the victims' families as they demand recognition and compensation.

"You have posted guards and sentries in front of the home of each victim's family, followed us closely, watched us, eavesdropped on our phone conversations, interfered with our computer communications, and opened and confiscated our mail," the essay says. "You have even arbitrarily detained us, arrested us, searched our homes and confiscated our possessions, frozen donations to us, and deprived the freedom of movement of relatives of the victims."

Now the passage of time is setting limits of its own.

"I'm in my 80s and my husband is in his 90s, and we're the oldest parents," said Li Xuewen, whose son was a 28-year-old graduate student planning to go abroad when the crackdown occurred.

"My husband is in critical condition at a hospital, and I'm even unable to visit my son's tomb this year," Li said.

But "we are clear in mind and we will hold on," she said by phone Wednesday, her voice calm and firm.

Young people in China know little about the Tiananmen events, but the issue shimmers below the surface.

One of China's most assertive state-controlled newspapers published a cartoon Tuesday showing a little boy drawing a line of tanks on a blackboard, with what looked like a soldier standing in front.

It was part of a package for International Children's Day, but the image was quickly passed around online with comments on the crackdown - then quickly removed from the paper's website.

One of Tiananmen's most enduring images is of a man standing in front of a line of tanks in the heart of Beijing and trying to block their way.

As authorities again pressured people inside China to prevent Tiananmen-related events, those in exile are choosing to mark the day on Twitter. Wang Dan, the student leader who topped the most-wanted list after the crackdown, said in an e-mail statement Wednesday that he would be tweeting along with the second-most-wanted, Wu'er Kaixi, and fellow student organizer Chen Ziming.

The goal, Wang said, is to "express our determination that we will never forget Tiananmen."

In Beijing, the victims' parents, many well into their 70s, are running out of time to remember. Zhang said some had been privately approached by young people in China who say they secretly support their cause.

"That makes us feel a little relieved," she said. "The authorities want to pull us down until we're all dead, but even if a tree is dead, its seed will grow eventually."