Linking problem in assembly code

Here is my assembly code:

-asm
.section .data
	mystring: .asciz	"Hello world\n"

.section .text
.globl	_start
_start:

pushl	$0
pushl	$mystring
call	printf

pushl	$0
call 	exit

I am trying to assemble and link this code in my 64 bit ubuntu machine **in 32 bit mode**. This code is assembled successfully with this command :

-shell
as -32 demo.s -o demo.o

but when i try to link it with ld command :

-shell
ld -m elf_i386 -s demo.o -o demo -lc

its giving this error :

ld: skipping incompatible /usr/lib/x86_64-linux-gnu/libc.so when searching for -lc
ld: skipping incompatible /usr/lib/x86_64-linux-gnu/libc.a when searching for -lc
ld: cannot find -lc: No such file or directory
ld: skipping incompatible /usr/lib/x86_64-linux-gnu/libc.so when searching for -lc

What should I do for this? This is my libc.so locations:

libcjson.so.1 (libc6,x86-64) => /lib/x86_64-linux-gnu/libcjson.so.1
	libc.so.6 (libc6,x86-64) => /lib/x86_64-linux-gnu/libc.so.6
	libc.so.6 (libc6) => /lib/i386-linux-gnu/libc.so.6