**Exhibit 12.1****CERTIFICATION****Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002**I, Ku-Taek Lee, the Chief Executive Officer and Representative Director of POSCO, certify that:1. I have reviewed this annual report on Form 20-F of POSCO; 2. Based on my knowledge, this report does not contain any untrue statement of a material factor omit to state a material fact necessary to make the statements made, in light of thecircumstances under which such statements were made, not misleading with respect to the periodcovered by this report; 3. Based on my knowledge, the financial statements, and other financial information included inthis report, fairly present in all material respects the financial condition, results ofoperations and cash flows of the company as of, and for, the periods presented in this report; 4. The company’s other certifying officer and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e))and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and15d-15(f)) for the company and have: (a) Designed such disclosure controls and procedures, or caused such disclosurecontrols and procedures to be designed under our supervision, to ensure that materialinformation relating to the company, including its consolidated subsidiaries, is madeknown to us by others within those entities, particularly during the period in which thisreport is being prepared;  (b) Designed such internal control over financial reporting, or caused such internalcontrol over financial reporting to be designed under our supervision, to providereasonable assurance regarding the reliability of financial reporting and the preparationof financial statements for external purposes in accordance with generally acceptedaccounting principles;  (c) Evaluated the effectiveness of the company’s disclosure controls and procedures andpresented in this report our conclusions about the effectiveness of the disclosurecontrols and procedures, as of the end of the period covered by this report based on suchevaluation; and  (d) Disclosed in this report any change in the company’s internal control overfinancial reporting that occurred during the period covered by the annual report that hasmaterially affected, or is reasonably likely to materially affect, the company’s internalcontrol over financial reporting; and5. The company’s other certifying officer and I have disclosed, based on our most recentevaluation of internal control over financial reporting, to the company’s auditors and theaudit committee of the company’s board of directors (or persons performing the equivalentfunctions): (a) All significant deficiencies and material weaknesses in the design or operation ofinternal control over financial reporting which are reasonably likely to adversely affectthe company’s ability to record, process, summarize and report financial information; and  (b) Any fraud, whether or not material, that involves management or other employees whohave a significant role in the company’s internal control over financial reporting.   Date: June 27, 2007     /s/ Ku-Taek Lee Ku-Taek Lee  Chief Executive Officer and Representative Director