Grid ans testng

I need to divide to run test on paralel in two nodes ( 500 in each node)
Nodes: 2

I mean 1000 java files and each file there is only one test

SuiteA.xml contains 500 class file
SuiteB.xml contains 500 class file

in tesng.xml i have used parallel=tests, now SuiteA and SuiteB will run serially but tests in SuiteA runs parallel after finishing the tests , SuiteB test will run parallel.

What i need:
SuiteA and SuiteB should run parallel , but tests in them should run serially. what i need to configure in xml?