House Minority Leader Nancy Pelosi ridiculed the latest Republican changes to a bill to repeal and replace Obamacare as ineffective at ensuring coverage for those with pre-existing conditions.

"It's a joke," Pelosi, D- Calif., said a news conference condemning the GOP's American Health Care Act, which could receive a vote by this weekend.

Pelosi and Democrats have been holding public events to criticize the bill almost every day in an effort to kill the building GOP momentum in favor of the plan, which would repeal many of the Obamacare mandates and allow states to receive waivers for coverage requirements.

"This is deadly," Pelosi said.

Pelosi took a swing Wednesday at Rep. Fred Upton, R-Mich., a centrist Republican who on Wednesday shifted his vote to a "yes" after a modification aimed at ensuing coverage for people who are sick.

The change would provide $8 billion over five years to help those with pre-existing conditions afford coverage. But Pelosi said the money was far from enough. It would cost $200 billion over a decade to adequately cover people with pre-existing conditions, she said.

Upton, Pelosi told reporters, is using "some fake reason" to vote for the bill, that will "make it look like the bill is better."

But Pelosi said the change "doesn't improve the bill."

The news conference featured people with pre-existing conditions who said that without Obamacare, they would have lost coverage.

Pelosi is working to prevent the repeal of Obamacare, which was her signature legislative achievement during her time as House speaker. The law is suffering from a collapse of the insurance marketplace, skyrocketing premiums and climbing deductibles.

Pelosi did not address the problems with Obamacare during the news conference.

Democrats have waged a successful campaign in getting those covered by the law to vocally oppose its repeal.

"The communications we are receiving are from the American people calling into Congress and saying stop," Pelosi said. "They are threatening devastation in the lives of the American people."