WASHINGTON (Reuters) - Congress should move quickly with an $8 billion sale of F-16 fighter jets to Taiwan as the self-ruled island faces pressure from China’s increased military presence in the region, leading U.S. Democratic and Republican lawmakers said on Friday.

FILE PHOTO: A U.S. Air Force F-16 fighter taking part in the U.S.-led Saber Strike exercise flies over Estonia June 6, 2018. REUTERS/Ints Kalnins/File Photo

China denounced the planned sale, one of the biggest yet by the United States to Taiwan, which Beijing considers a renegade province. It warned of unspecified “countermeasures.”

Senate Foreign Relations Committee Chairman Jim Risch, a Republican, welcomed the proposed sale of the Lockheed Martin Corp LMT.N F-16V jets. "These fighters are critical to improving Taiwan's ability to defend its sovereign airspace, which is under increasing pressure from the People’s Republic of China," he said in a statement.

The chairman of the Senate Armed Services committee, Jim Inhofe, and fellow Republican Senator John Cornyn said Taiwan “remains an important pillar of security and stability” in the region. The sale of the jets would “deter aggression given Beijing’s increasing assertiveness and military buildup,” they said in a joint statement.

Similarly, the Democratic chairman of the House of Representatives Foreign Affairs Committee, Eliot Engel, and the panel’s ranking Republican, Michael McCaul, said in a joint statement that the deal “sends a strong message” about U.S. commitment to security and democracy in the region.

Senators Marco Rubio and Ted Cruz, both Republicans, also issued statements backing the deal.

Washington has no formal ties with self-ruled and democratic Taiwan but is bound by law to help provide it with the means to defend itself. It is the main arms supplier to Taiwan and there is broad support for this in Congress.

China has never renounced the use of force to bring Taiwan under its control and has repeatedly denounced U.S. arms sales to the island.

Friday’s New York Times quoted unnamed U.S. officials as saying that the Trump administration, which is engaged in a major trade war with China, was moving forward with the sale and said the State Department gave informal notification of the plan to the House and Senate foreign affairs committees on Thursday.

The paper said once those committees gave the go ahead, which would probably come within days or weeks, there would follow a formal notification to Congress, which would trigger a 30-day period for objections.

The State Department and White House declined to comment.

China’s Foreign Ministry spokeswoman Hua Chunying said Beijing had made solemn representations to the United States over the planned sale.

China’s state-run Xinhua news agency quoted Hua as saying that it was a serious violation of the “one-China principle,” under which Washington recognizes Beijing and not Taipei, and undermined China’s sovereignty and security interests.

Hua urged the U.S. to stop arms sales to and military contact with Taiwan, otherwise, the Chinese side would “certainly take countermeasures,” Xinhua said.

After the United States approved sales of tanks and Raytheon Co's RTN.N anti-aircraft Stinger missiles to Taiwan in July, China said it was "ready to go to war" if people "try to split Taiwan from the country."

Beijing said it would impose sanctions on U.S. companies involved in any deals.

On Thursday, Taiwan unveiled its largest defense spending increase in more than a decade, to T$411.3 billion ($13.11 billion.)