WASHINGTON - The United States is renewing a call that all nations including the U.S. and China "must raise their ambitions" on carbon neutrality, as officials from the world's two largest emitters held talks in Shanghai on Thursday.

U.S. officials and analysts say Special Presidential Envoy for Climate John Kerry's consultations with his Chinese counterparts this week are paving the way for next week's virtual Leaders Summit on Climate, but caution against a quick breakthrough.

"We must insist Beijing do more to reduce emissions and help tackle the worldwide climate crisis," said a State Department spokesperson who spoke to reporters on condition of anonymity.

The spokesperson added China "is not yet on a path that will allow the world to meet the Paris Agreement's goal of holding the increase in the global average temperature to well below 2 degrees Celsius and pursue efforts to limit the temperature increase to 1.5 degrees Celsius."

"Of course, it's not going to be easy," said Jane Nakano, a senior fellow in the Energy Security and Climate Change Program at the Washington-based Center for Strategic and International Studies (CSIS).

Nakano said Thursday that many countries, not just the U.S., "are hoping to see much more clear articulation [on] how China plans on reducing its emissions level."

In Beijing, officials gave few details on Kerry's talks with China's special envoy on climate change, Xie Zhenhua.

"I don't have any information to offer," Zhao Lijian, a spokesperson from China's Ministry of Foreign Affairs, said Thursday.

Chinese President Xi Jinping is among the 40 world leaders invited to attend the climate summit on April 22-23.

The invitation comes as relations between Beijing and Washington are at their most strained for decades because of clashes over Xinjiang, Hong Kong, Taiwan, the South China Sea, regional security and China's economic coercion of U.S. allies.

In a recent interview with The Wall Street Journal, Kerry said the U.S. is not wrapping the climate issue into talks on other topics that the U.S. and China disagree on.

"We're not trading something to do with the planet and health and security for something else that's more of a political or ideological difference or a practical difference in the marketplace," said Kerry.

Some analysts say the Biden administration is so far separating its concerns about climate change from the region's key issues such as China's reported human rights violations and increasing territorial aggression.

"I see no evidence of" the U.S. compromising its geopolitical competition with China while seeking a cooperation on climate change, said Mike Green, senior vice president for Asia and Japan Chair at CSIS and a former White House National Security Council staffer.

Green said he is not ruling out a possible pull-aside virtual meeting between Biden and Xi.

"We have a big agenda with China," Green said Thursday. "My guess is probably that there will be a pull-aside" virtual meeting in a businesslike fashion.