The phrase "additional agreement" is correct and usable in written English.
It can be used when referring to a supplementary contract or understanding that adds to an existing agreement.
Example: "The parties have reached an additional agreement regarding the terms of payment."
Alternatives: "supplementary agreement" or "further agreement".
But Tehran gave no indication when it would suspend uranium enrichment or sign, ratify and carry out an additional agreement under the Nuclear Nonproliferation Treaty of 1968 that would allow surprise inspections of its nuclear installations.
However, the second document shows that the DNC and Clinton campaign had an additional agreement which provided the campaign with influence over the DNC well before Clinton won the nomination.
3. In appropriate cases of research carried out on a group of persons or a community, additional agreement of the legal representatives of the group or community concerned may be sought.
On completion of the required period of service under an agreement under subsection (d), the borrower and the Secretary may, subject to paragraph (2), enter into an additional agreement in accordance with subsection (d).
The Indo-Russian joint venture was set up on Nov. 20, 1988, with an additional agreement signed on June 21 , 1998
Chances are that the most likely way to "cure the defects" would be an additional agreement between Google and Motorola that allows Motorola to move forward with this litigation.
She has not ruled out the possibility of pursuing additional agreements if she is elected president.
Both unions hope to negotiate additional agreements to bring them up to the current year and beyond.
An MoD spokesman said additional agreements with contractors for support functions such as testing, training and spare parts had pushed the cost up.
With the treaty in place, additional agreements were reached that limited, then sharply reduced, the number of offensive missiles on both sides.
He said that the borrowers had signed agreements to repay 40 percent of the money, about $216 million, and that additional agreements were being negotiated.
