China has sent warships and fighter planes close to Taiwan during a visit by US treasury secretary Janet Yellen to Beijing aimed at easing strained relations. 

Taiwan’s defence ministry said it was monitoring the situation, which involved 13 aircraft and six vessels, and land-based missile systems were ready to respond.

Four of the planes, including two SU-30 jet fighters, crossed the median line in the Taiwan Strait, which serves as a de-facto border between the sides.

China claims Taiwan as its own territory, to be reclaimed by force if necessary, and sends air and naval missions on a regular basis.

US support for the self-governing island republic, which split from mainland China during a civil war in 1949, remains a major stumbling block to ties with Beijing.

Shortly before Ms Yellen’s arrival, Chinese President Xi Jinping visited the eastern headquarters of the People’s Liberation Army.

Its area of operations directly faces the island across the Taiwan Strait.

Xi calls for ‘enhanced war planning’

Addressing commanders at the Jiangsu province headquarters on Thursday, Mr Xi “stressed efforts to … break new ground for theatre command development and war preparedness,” state media reported.

He called for “enhancing the planning of war and combat… and stepping up training under real combat conditions to raise the forces’ capabilities to fight and win,” the reports said.

Beijing also strongly objects to US military support for Taiwan, and recently criticised an upcoming $440m (£343m) sale of cannon shells and other equipment, accusing Washington of turning Taiwan into a powder keg.

US stresses potential for China ties

Ms Yellen is not expected to meet with Mr Xi during her visit.

During talks with top officials, she has said the world’s two biggest economies must compete fairly and
communicate closely to avoid misunderstandings.

She told vice premier He Lifeng that a record for two-way trade set last year despite recent tensions showed there is “ample room for our firms to engage in trade and investment”.

Ms Yellen said: “Amid a complicated global economic outlook, there is a pressing need for the two largest economies to closely communicate and exchange views on our responses to various challenges.”

Doing so could “help both sides more fully understand the global economic outlook and make better decisions to strengthen our economies”, she said.

Ms Yellen restated that Washington is not seeking a winner-takes-all approach or economic advantage in its relations with China, but wanted to ensure a healthy competition with a “fair set of rules” that would benefit both countries.

She urged China not to allow any disagreements to “lead to misunderstandings, particularly those stemming from a lack of communication, which can unnecessarily worsen our bilateral economic and financial relationship”.