The phrase "all efforts to conclude" is correct and usable in written English.
It can be used when discussing attempts or actions taken to reach a conclusion or finalize something.
Example: "We are making all efforts to conclude the negotiations by the end of the week."
Alternatives: "all attempts to finalize" or "all actions to reach a conclusion".
Had United said no, it would have left itself vulnerable to a lawsuit by US Airways charging that it had not fulfilled their merger agreement's stipulation that both sides make "all reasonable efforts" to conclude the deal.
He did not back Chamberlain's unsuccessful efforts to conclude an alliance with Germany (1898 1901).
A Shorten Labor government will redouble efforts to conclude good faith negotiations with Timor-Leste to settle the maritime boundaries between our two countries.
Not merely should these moves be condemned but, through the auspices of the WTO, there should be renewed efforts to conclude the Doha round of trade negotiations.
Efforts to conclude a widely acceptable multilateral agreement on traffic rights were unsuccessful, and such rights have continued to be handled through bilateral international agreements.
F.B.I. agents have visited Irian Jaya on several occasions but have been frustrated in efforts to conclude an investigation by lack of cooperation by the Indonesians, a senior American official said.
Both sides initially believed this failure was only temporary, and Mr. Barak and Mr. Arafat continued serious efforts to conclude a peace deal for another two months, until the outbreak of violence in September.
We'll redouble our efforts to conclude a high-quality, comprehensive Trans-Pacific Partnership agreement.
To achieve this he will be open to dialog with the Arab and Muslim world and will endorse efforts to conclude national unity," he said.
Mursi said, according to the reports, that "efforts to conclude a truce between the Palestinian and Israeli sides will produce positive results in the next few hours".
