The United States has launched the formal process to get account details of 4,450 American clients of UBS suspected of tax evasion, the Swiss finance ministry said on Monday.

Switzerland agreed to reveal the names to U.S. authorities in a tax dispute settlement that pierced Swiss banking secrecy.

The finance ministry said the United States had asked for administrative assistance from Swiss authorities.

In accordance with the agreement, the FTA (Swiss Federal Tax Administration) must now issue a conclusive decree on surrendering the information requested in the initial 500 cases within 90 days, the finance ministry said.

For the remaining conclusive decrees, there is a deadline of 360 days.

UBS must provide the client information mentioned in the request for administrative assistance and prepare it for processing by the FTA, the ministry said.

UBS had undertaken to do so in a separate agreement with the U.S. tax authority, it said.

The persons concerned had the right to appeal against the final decree, the finance ministry said.

The UBS dispute strained relations between the United States and Switzerland and challenged the latter's jealously guarded bank secrecy laws.

The row also weighed heavily on UBS, which is trying to rebuild its once powerful brand after record losses caused by the subprime crisis.

U.S. investor Capital Group Companies has taken a 4.38 percent stake in UBS, an announcement on the Swiss stock exchange website from Saturday showed.

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(Reporting by Sven Egenter; Editing by Dan Lalor)