The United States is "weaponizing" visas, having failed to grant them in time or at all for Chinese space officials for an international event in Washington, China's Foreign Ministry said on Wednesday, in the latest escalation of tensions between the two countries.

China and the United States are locked in a bitter trade dispute, which they are currently trying to resolve, and also have deep disagreements on many other areas, including human rights, the disputed South China Sea and Chinese-claimed Taiwan.

Chinese Foreign Ministry spokeswoman Hua Chunying said a Chinese delegation had wanted to take part in the ongoing International Astronautical Congress being held in Washington.

China is an important participant in the congress and sends delegations every year, she added. China hosted the congress in 2013. Last year, it was held in Germany.

China had applied for the visas in July, and on Oct. 12 the delegation from the China National Space Administration went for visa interviews at the U.S. embassy, but the head of delegation still did not have his visa as the congress began, Hua said.

"This caused the Chinese delegation to be unable to attend the opening of the International Astronautical Congress," Hua said, adding that several other Chinese delegates also did not get visas.

The U.S. embassy said it was unable to discuss individual visa cases as they were confidential under U.S. law. The State Department did not immediately respond to a request for comment.

At the International Astronautical Congress on Monday, Wu Yanhua, vice chairman of the China National Space Administration, was the only official absent from a panel of other heads of space agencies from Germany, Russia, India, the United States, France and Japan.

The panel moderator said his absence was due to a "scheduling conflict" and a conference spokeswoman said, "he was invited, but could not make it, which we regret very much."

Hua said the issue was just the tip of the iceberg, with the United States stepping up denial, delay or cancellation of visas for Chinese academics, students and scientists.

The United States has also gone against United Nations rules by denying visas for Russians and Iranians to participate there, she added.

"The United States is weaponizing the visa issue, repeatedly disregarding its international responsibilities and obstructing normal international exchanges and cooperation."

China urges the United States to change its ways, Hua said.

Russia recently complained to the United Nations that the United States did not grant visas "to a number" of its delegates, including members of the Russian parliament, to attend meetings of the U.N. General Assembly and its committees and for a Comprehensive Nuclear-Test-Ban Treaty conference.

In a Sept. 30 letter to U.N. Secretary-General Antonio Guterres, seen by Reuters, Russian U.N. Ambassador Vassily Nebenzia accused Washington of violating its obligations as the host country for the world body's headquarters.

Under the 1947 U.N. "headquarters agreement," the United States is generally required to allow access to the United Nations for foreign diplomats. But Washington says it can deny visas for "security, terrorism, and foreign policy" reasons.

Advancing China's space program is a priority for Beijing, with President Xi Jinping calling for the country to establish itself as a space power, and apart from its civilian ambitions Beijing has tested anti-satellite missiles.

China insists its space program is for peaceful purposes, but the U.S. Defense Department has highlighted its increasing space capabilities, saying it was pursuing activities aimed to prevent adversaries from using space-based assets in a crisis.