One hassle of traveling out of the country is making sure your phone is ready for the trip too.

Google's experimental wireless service, called Project Fi, already works for US users traveling abroad, without requiring them to pay more for international plans. But on Tuesday, the search giant said it wants to sweeten the pot for people using Fi while traveling by revving up international data speeds. (Google still doesn't offer Fi to users based outside the US.)

It's the latest perk rolled out by Project Fi, which has been able to undercut traditional carriers by letting people switch between cellular service and Wi-Fi signals automatically and without dropping a call or disrupting a streaming video. Google uses Project Fi, which runs on the Sprint, T-Mobile and US Cellular networks, to test models and services that it hopes the greater wireless industry will adopt.

Now playing: Watch this: Getting to know Google's wireless service, Project Fi

The service is part of a broader initiative by Google to provide more wireless access to more people. Project Fi joins Google Fiber, its program to sell super-fast internet service, and Project Loon, which uses balloons to rain down Wi-Fi signals in rural areas. Google is one of several companies, including Facebook, angling to connect more people to the internet and, potentially, to their services.

Project Fi costs $20 a month for voice, text, Wi-Fi tethering and international coverage. Each gigabyte of data costs $10 per month. But if you don't use all of the data you buy for the month, Google refunds you for what you didn't use.

Google said only 20 percent of Americans use cellular connections when they travel abroad because the service is so slow, according to a survey the company conducted in June. With Fi's update, international data speeds will be 10 to 20 times faster, the company said. To strengthen its coverage, Google added has added the international carrier Three to its Fi network.

The company also said it's expanding international coverage to more than a dozen new countries and territories, including the Bahamas, Montenegro and Macao.

There's a big catch for Google Fi, though. Right now, it works only with a small number of phones designed by Google, including the Nexus 5X and 6P. Sorry, iPhone users, you're out of luck. To try to entice more customers, Google said it will be shaving $150 off the Nexus 6P for the next week when they buy and activate Fi.

Project Fi is an important experiment for Google, but it is just that. Before Fi launched, the company said it doesn't intend to become a full-blown wireless carrier.