Rihanna is feeling the pressure to throw the best bachelorette party ever for her pop pal Katy Perry, because she wants the pre-wedding celebrations to be as elaborate as the nuptials themselves.

The "Umbrella" beauty has taken on the responsibility of planning Perry's last big party as a single girl before she marries Russell Brand, but Rihanna admits it's proving to be hard work.

She tells "Access Hollywood," "It's taking up way more time than my tour. It's so much pressure. Her wedding is going to be the best wedding I've ever been to.

And now I have to match the bachelorette party to that!" Perry is due to exchange vows with Brand later this year, although details about their wedding plans have yet to emerge.