ZURICH (Reuters) - Swiss financial regulator FINMA has specified the central elements of its regulatory requirements for the merged UBS and Credit Suisse, it said on Monday.

The regulator also said it "welcomes UBS's strategic focus, which foresees a rapid reduction of risk in investment banking," in a statement after UBS formally completed its emergency takeover of its stricken rival.

FINMA said it would continue to supervise the merged bank 'very closely' during the integration process.

"The legal consummation of the merger between UBS Group and Credit Suisse Group marks the end of a phase of great uncertainty," FINMA said in a statement. "This creates clarity and stability."

The regulator said one of the most pressing goals for the new merged bank was to quickly reduce the risk of the former Credit Suisse investment bank, but was confident this could be achieved.

"Following the completion of the transaction, the merged bank has the necessary capital and liquidity resources to carry out these risk reduction activities quickly and decisively and to successfully complete the integration," FINMA said.

Switzerland's largest bank became even bigger on Monday after it announced it has completed its acquisition of Credit Suisse, following a government-backed rescue earlier this year.

The combined bank has a balance sheet of $1.6 trillion and oversees $5 trillion of assets, giving UBS overnight a leading position in key markets it would otherwise need years to grow in size and reach. UBS has said the combined bank will be the will "undisputed leader in Switzerland."

The mega-bank will employ 120,000 worldwide, although it has already announced it will in the future be cutting jobs to take advantage of synergies and reduce costs.

(Reporting by Noele Illien, editing by John Revill)