The phrase "while announcing that" is correct and usable in written English.
It is typically used when introducing a statement that was recently declared, especially in the context of a speech or other formal address. For example, "The mayor announced a city-wide curfew while announcing that the current health situation was dire."
And then, on Friday, the day that Great Britain declared its exit from Europe, Donald Trump arrived in Scotland, to survey the regal glories of the Trump Turnberry golf course, in Ayrshire, while announcing that Brexit was a "great victory".
Italian authorities released the video while announcing that alleged gangsters affiliated with the organization throughout northern Italy were arrested and charged with various crimes, including illegal weapons sales and extortion.
While announcing that one is relinquishing power can make a politician a lame duck, it is not necessarily debilitating in the Senate.
Last week while announcing that he planned to stand for mayor of London, Galloway insisted a legal challenge to the Bradford West result was still in play.
When Mr. Bush's counterterrorism policies were revealed by the news media, Mr. Thiessen wrote a speech for the president defending them while announcing that he would empty secret C.I.A. prisons.
A week later, Apple issued an official admission that it had made a mistake, while announcing that it was rejoining Epeat, which had given the MacBook Pro a Gold6 rating.
As for the artist's genes, there was a news story a while back announcing that a celebrity singer had decided to impregnate herself with the sperm of a rock star.
While in Montrouge, Cazeneuve announced that army reinforcements would be called in over the next two days to protect Jewish schools and places of worship from antisemitic attacks.
While tweeters were rushing to announce that Knox was "guilty", oops, we mean "not guilty", so was the mainstream media.
News about the rally was also broadcast by the Shanghai radio station, which informed people about the march while also announcing that it was unauthorised.
This kind of pressure "could support" a finding of a rules violation, the panel said, while carefully announcing that no further action would be taken.
