David Sullivan has revealed West Ham wanted to sign Sam Byram this summer but, after realising Everton moved for him last week, it was "now or never" to get their man.
And Sullivan confirmed to Sky Sports News HQ on Tuesday that both personal terms and a transfer fee have been agreed with all parties.
He said: "We hoped to sign Sam Byram in the summer when he was out of contract at Leeds.
"In the last few days, it looked like he was going to Everton, so we realised it was now or never and had to pitch in to sign him.
"Hopefully that will go through in the next 24 hours. Everything has been agreed with the player and the club.
"I wouldn't normally say this but the Leeds chairman has made it public, because I think it's wrong to mention what you're doing until it's done. But if they're happy to mention it, so are we."
Sullivan believed his club would not do any business in the winter transfer window but he also revealed they are looking to bring in a striker on loan.
There's a possibility that a striker will come in on loan.... He's an overseas striker. If I told you, you wouldn't believe it.
"We are looking, long-term, for a 20-goal-a-season striker," he said.
"There's a possibility that a striker will come in on loan, with the option to buy, within the next seven days. He's an overseas striker.
"If I told you, you wouldn't believe it. I can't tell you which league because then you'll know exactly who it is.
"We are signing from a very strange league. But he has played in higher leagues."