在买方出具的付款保函（“Payment Guarantee”）第一段有描述：

with SELLER’s Hull No. ____ ("the VESSEL"), we, _______, hereby IRREVOCABLY, ABSOLUTELY and UNCONDITIONALLY guarantee, as the primary obligor and not merely as the surety, the due and punctual payment by the BUYER of each and all of the 2nd,the 3rd and, and 4th instalments of the Contract Price amounting to a total sum of United States Dollars (US$ ) as specified in (2) below.

明确买方担保人作为第一债务人，不可撤销的、绝对的、无条件地承担...，而在卖方银行出具的还款保函中并没有同样的描述。买方在合同谈判中提出合同对等的原则，要求将买方付款保函中“ABSOLUTELY and UNCONDITIONALLY”删除。

首先，从商务角度来说，合同买方，尤其是合同买方是单船公司时，合同买方是没有足够的资产负担合同条款下的付款义务。合同买方的母公司不仅仅是担保人，而且是实际买方，有无条件的付款义务。而卖方银行作为卖方违约时还款的担保人，并非合同主体，是合同第三方存在。银行的还款义务并不是无条件的。

从法律条款解释：如删除买方付款保函中“UNCONDITIONALLY”的描述，会给船东“possible defense，this guarantee is conditional,”，即造船合同若有纠纷需要按造船合同先解决，不能发生纠纷就直接走保函。例如，船东“fails to make payment, unconditional guarantee”项下可以直接找担保方要钱；“conditional guarantee”项下船东可能“argue”是由于船厂先有“default”我们才未付款，这时就不能找担保方要钱，只能先按造船合同争议解决后才可以。

反之如果卖方还款保函中加入“UNCONDITIONALLY”的描述，还款保函将成为见索即付而绕过仲裁条款的保函。

“The requirement of "to unconditionally guarantee" is to avoid the dispute that the guarantee issued by the guarantor is conditional on some cirucmstances which could be that the terms of the SBCshould not be changed or no fraudlent performance should be committed by either of the party to the SBC or whatsoever the Guarantor belive would enable it to avoid the obgliation under the letter of guarantee.  "to unconditionally guarantee" is different from the requirements as described in the mainbody of the letter of guarantee. That is to say, even if the requirements have been satisfied, the guarantor may also claim that it"s guarantee undertaking is conditional.”