The Trump presidency on Feb. 15 at 4 p.m. EST

(Reuters) - Highlights of the day for U.S. President Donald Trump's administration on Wednesday:

RUSSIA

Senior Republicans issue their boldest challenge yet to Trump, promising to get to the bottom of the relationship between his aides and Russia, and calling for ousted national security adviser Michael Flynn to testify before Congress.

The Trump administration offers the job of national security adviser to U.S. Vice Admiral Robert Harward, sources say, but it is not clear if he accepted.

The Kremlin says U.S. media reports about Russian intelligence connections to Trump's presidential campaign are groundless.

Russia also says it will not return Crimea to Ukraine or discuss the matter with foreign partners after the White House says Trump expects the annexed Black Sea peninsula to be

returned.

CABINET AND ADMINISTRATION

Trump's choice to head the Labor Department, Andrew Puzder, withdraws his name from consideration amid mounting concerns he would not have enough votes for confirmation.

Trump's choice of Representative Mick Mulvaney to become White House budget director on Wednesday appeared to pick up enough Republican votes to vault him into the job.

NETANYAHU

Trump drops U.S. insistence on a two-state solution to the Israeli-Palestinian conflict, a long-standing bedrock of Middle East policy, even as he urges Israeli Prime Minister Benjamin Netanyahu to curb settlement construction.

BUSINESS

Trump says tax code revisions are a critical way to boost the nation's economy as he kicks off a White House meeting with chief executive officers of Target Corp, Best Buy Co Inc and six other major retailers.

FOREIGN POLICY

Trump's defense secretary seeks to reassure NATO of steadfast U.S. support at talks in Brussels as nervous European allies try to look past the president's rhetoric and the turmoil within his administration.

U.S. Secretary of State Rex Tillerson is heading to Bonn to interact with counterparts from the Group of 20 top economies at a time many are wondering how strongly Trump's "America First" message will reshape U.S. foreign policy.

Vice President Mike Pence also is bound for Europe this week to meet with allies seeking clarity on the administration's foreign policy strategy and its stance toward Russia.

OBAMACARE

The Trump administration proposes changes to the Obamacare individual insurance market that insurers welcome as a good start but that others say could raise consumers' out-of-pocket cost.

(Compiled by Bill Trott; Editing by Peter Cooney and James Dalgleish)