formatting print statements with multiple lines

When executing the command:

    print(cat(paste("Input criteria does not meet specifications.  Check
input against the following requirements:
            a >= 0
            b <= 0
            c >= 0 ", sep=""), ""))

I get:
Input criteria does not meet specifications.  Check input against the
following requirements:
            a >= 0
            b <= 0
            c >= 0  NULL
(with that extra NULL at the end).

If I omit the 'cat' command, the NULL goes away, but I no longer get the
next-line formatting that I want.

I think I'm missing something about one of these functions returning a NULL
value, but I can't seem to get the exact result I want (no NULL value, and
keep the next-line formatting.)

Any ideas or suggestions are much appreciated.

Thanks!

	[[alternative HTML version deleted]]