Aitor Karanka says Middlesbrough are speaking to a number of Premier League clubs - including Chelsea - about making further new signings.
Karanka has already brought in seven new faces this summer but remains keen to boost his squad after admitting an interest in a loan deal for Chelsea striker Patrick Bamford.
Bamford would become the second player to arrive from Stamford Bridge this summer after already securing defender Kenneth Omeruo on loan, while Nathaniel Chalobah was loaned to the Riverside last season.
Karanka has a strong relationship with Blues boss Jose Mourinho following their time together at Real Madrid, but the Spaniard says they are looking to do business with other top-flight teams as well.
"We are working until the last day (of the transfer window) because at the minute we haven't got the squad we want, but I'm happy with the performances of the players I have now," he told the Evening Gazette.
"We are working not just with Chelsea, but with other big teams in the Premier League. Our link with Chelsea is good because everyone knows my relationship with Jose, but it's not just with him.
"I would like to finish (transfer business) before the deadline but sometimes you have to wait until the last second.
"I want to finish this transfer window with all the players I wanted two or three months ago. If we do that I'll be very happy."