The phrase "announce that while" is correct and usable in written English.
It can be used when introducing a statement or declaration that includes a condition or contrast.
Example: "We would like to announce that while the event will proceed as planned, we are taking additional safety measures."
Alternatives: "declare that although" or "state that while".
This week the company announced that while Sony's worldwide music revenue of $5.268 billion for fiscal 2003 would continue to decline over the next year, it expected adjusted earnings before interest, taxes, depreciation and amortization to improve slightly from last year's $454 million.
Salesforce has responded to cries of foul play in its $1 million hackathon by announcing that while winning team Upshot didn't cheat, judges weren't given sufficient information to select a winner so it's giving $1 million to each of the top two finalists, Upshot and Healthcare.love.love
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.
Then he announced that while Thursday's practice would be held in the afternoon, he wanted them to stay home Wednesday night.
Osborne recently announced that while he had hoped austerity could end by 2015, it now looks as if the policy will continue until at least 2018.
Earlier this week, he announced that while he supported the "goals and aspirations" of the boycott, he could not run for president "if I can't campaign effectively".
Thomas de Maizière, the German interior minister, announced that while Austria was the focus of the new border controls, all of Germany's borders would be affected.
On Tuesday the station announced that while Triple J would celebrate 2017's Australia Day with the Hottest 100, future years were under review.
Afterward, he announced that while his mind had not been changed on the issues, he was a "better person" for listening.
