US will act if threatened: Biden tells China

US President Joe Biden cited the shooting down of a Chinese spy balloon last week to warn Beijing that Washington "will act" if its sovereignty was threatened.

Delivering his second State of the Union address, an annual homily by a US President of past achievements and future plans, Biden used the shooting of the balloon -- without going into specifics -- to engage in some saber-rattling at Beijing even as sought to frame the relationship with China as a competition rather than a conflict.

"As we made clear last week, if China threatens our sovereignty, we will act to protect our country. And we did," he said in his address on Tuesday night.

He went on to rub it in and added "name me a world leader who'd change places with (Chinese President) Xi Jinping... Name me one! Name me one!".

The suspected Chinese spy balloon which was shot down by an American F-22 fighter jet over the Atlantic Ocean on February 4.

US defence officials had first announced they were tracking the "strange object" on February 2, and waited until it was safely over water before shooting it down.

The officials described it as a violation of American sovereignty and internal laws.

Debris of the balloon and its payload were salvaged off the coast of Myrtle Beach in South Carolina a day after it was shot down.

The development came at a time when the two countries were moving to put the relationship on an even keel, building on the first in-person summit between Biden and Xi on the sidelines of the G20 summit in Bali.

US Secretary of State Antony Blinken immediately called off his weekend visit to Beijing for wide-ranging talks, including a meeting with President Xi, even after China had expressed regret in a rare display of contrition -- it said the "airship" was meant to study weather and had strayed into American airspace.

In his Tuesday night address, other major foreign policy issue Biden addressed at some length was Ukraine.

He reiterated his administration's commitment to helping Ukraine "as long as it takes" amid Moscow's ongoing war against Kiev.

The US has sent billions worth of military equipment to help Ukraine defend itself in the face of Russian invasion, and he has rallied NATO and other allies to do the same.

"We united NATO and built a global coalition.We stood against (Russian President Vladimir) Putin's aggression," he said.

Biden's speech was aimed largely at the domestic audience with talk of him getting ready to announce his re-election bid for 2024.

Even as he touted his administration's achievements since he took office in 2021, Biden also issued an appeal for unity, and repeatedly asked the Republicans to work with him.