China's Commerce Ministry said Thursday that Beijing had agreed with Washington to lift existing trade tariffs between the two nations in phases.

"Over the past two weeks, the two negotiating teams had serious and constructive discussions and agreed to remove the additional duties imposed on each other's products in different phases after they make progress in reaching a deal," Gao Feng, a spokesperson for China's Commerce Ministry, said at a weekly briefing in Chinese.

"Both sides should simultaneously undo existing additional tariffs in the same proportion to reach phase one deal, and that is an important condition for signing a preliminary agreement," Gao said according to a CNBC translation.

The ministry spokesperson also said, "As for how much of the tariffs should be removed, the two countries can negotiate based on the content of the phase-one deal."

When asked Thursday evening about trade talks, White House spokeswoman Stephanie Grisham said in an interview with Fox News that the Trump administration is "very optimistic" the two sides "will reach a deal soon."

Fresh hopes for a phase one trade accord prompted U.S. stock index futures to rally Thursday morning, with Dow futures poised to open up more than 120 points.

Market participants had expected the two economic giants to sign a deal later this month, after both Washington and Beijing spoke of progress in talks late last week.

However, Reuters reported on Wednesday that a meeting between President Donald Trump and Chinese President Xi Jinping could be postponed until December — delaying a chance for the two leaders to sign an interim trade deal.

The world's two largest economies have imposed tariffs on billions of dollars' worth of one another's goods since the start of 2018, battering financial markets and souring business and consumer sentiment.

The Trump administration has been putting increasing pressure on Beijing to curb massive subsidies to state-owned companies and stop the forced transfer of American technology to Chinese firms.

But, analysts are skeptical that a phase one trade deal will effectively tackle these issues, suggesting the two economic powers will need a more comprehensive agreement before market sentiment can be boosted sustainably.

— CNBC's Grace Shao contributed to this story.