China has sent warplanes into the self-declared recognition zone of Taiwan’s air defense zone several times in recent months, an act that does not violate any international law but usually leads Taiwan to take preemptive defensive measures, including sometimes turning its fighters around. Chinese planes have not entered the island’s territorial airspace — the area that stretches 12 nautical miles from its coastline. The State Department called on China to stop bullying Taiwan. Pelosi is planning a trip to Taiwan in the coming weeks, according to three sources familiar with the planning process. While other members of Congress and former US officials have visited Taiwan this year, Pelosi will be the highest-ranking US lawmaker to visit Taiwan in 25 years. Then-Speaker Newt Gingrich traveled there in 1997. Tensions between Washington and Beijing over the Taiwan issue have risen in recent months. The Chinese Communist Party has long claimed democratically-ruled Taiwan as part of its territory and has repeatedly vowed to “reunify” the island of 24 million people — by force if necessary — even though it has never ruled it. The US has pledged to provide Taiwan with the means to defend itself, although recent arms sales to Taiwan have been slow to arrive, raising concerns among US lawmakers. The Chinese embassy in Washington referred CNN to statements by a State Department spokesman, stating strong opposition to a possible visit by Pelosi, when asked to comment on airspace concerns. The Financial Times was the first to report Pelosi’s plans to visit. President Joe Biden cited the US military’s concerns about Pelosi’s potential trip earlier this week. “I think the military thinks it’s not a good idea right now, but I don’t know what the situation is,” Biden said Wednesday when asked if it was a good idea for Pelosi to travel to the self-governing island. Col. Dave Butler, a spokesman for the Joint Chiefs of Staff, said the military “generally” informs decision makers about military assessments. “We talk about what adversaries might do, we talk about logistics and military plans and readiness,” Butler said. He declined to say whether or not Chairman of the Joint Chiefs of Staff Mark Milley has spoken with Pelosi about a proposed trip to Taiwan. Pelosi said it was important to show support for Taiwan on Thursday, but said she would not discuss any travel plans, citing a security issue. Pelosi said she had heard “jokes” about Biden’s comments about her possible visit, but said she had not heard anything directly from the President. “I think what the President was saying is that maybe the military was afraid of my plane being shot down or something. I don’t know exactly,” Pelosi said. State Department officials also have some concerns, two sources said. State Department spokesman Ned Price deflected questions about the trip Thursday, calling it “hypothetical” at this time. “I’m not going to offer any advice from the podium,” Price said when asked about the State Department’s position on her possible visit. Price reiterated that the Biden administration is still sticking to its one China policy, noting that the US does not have diplomatic relations with Taiwan but has a “robust informal” relationship with the island. Expressing his opposition to Pelosi’s possible visit, Chinese Foreign Ministry spokesman Zhao Lijian said on Tuesday that it would “seriously violate the one-China principle and the provisions of the three China-US joint communiqués and harm China’s sovereignty and territorial integrity.” integrity of China”. The spokeswoman for Taiwan’s official office in DC, Sabina Chang, told CNN that Taiwan “has not received any information regarding a planned visit to Taiwan by Speaker of the House Nancy Pelosi.” CORRECTION: This story has been updated to reflect that Chinese aircraft have entered Taiwan’s air defense identification zone but have not violated international law. CNN’s Barbara Starr contributed to this report.