The phrase "a steadfast partner" is correct and usable in written English.
You can use it to describe someone who is reliable and consistently supportive in a relationship or collaboration.
Example: "Throughout the years, she has proven to be a steadfast partner in both business and personal matters."
Alternatives: "a loyal companion" or "a reliable ally."
And as they do, we will be proud to stand with them as a steadfast partner.
The United States intends to remain a steadfast partner of Saudi Arabia to ensure the interests of our country, Israel and all other partners in the region.
For nearly eleven years now, he has been a steadfast partner, an enthusiastic collaborator, and an institutional citizen always focused on the progress of the FAS and the University.
For nearly two years, as part of President Obama's Afghan war strategy, an expanding embassy staff here and streams of visiting delegations have repeatedly insisted that the United States is a steadfast partner interested in stabilizing, not undermining, Pakistan.
On Tuesday Trump said the US would remain a "steadfast partner" of Saudi Arabia, despite saying that the Saudi crown prince, Mohammed bin Salman, may have known about the plan to kill Khashoggi, a US resident and Washington Post columnist.
She acknowledged that Egypt and other Middle Eastern states face a "hard path" in implementing political and economic reforms, but she said the United States will remain a steadfast partner.
The people of Israel need an end to terror and a reliable, steadfast partner for peace.
He was a loyal and steadfast partner and all of us appreciate his loyalty and dedication to our firm.
Canada has certainly been a steadfast security partner of the United States, but exempting the #1 supplier of imported steel could drastically alter the efficacy of any trade action.
Such is the case this week at the Village Vanguard, where Mr. Iverson and Mr. Anderson are working without their steadfast partner, the drummer David King.
Karl beats, abuses, and steals from Candy, but Candy's omnipotent fantasy continues to see Karl as some kind of steadfast partner whom he has chosen.
